warm start - have to hit the gas

I'm still trying to sort out the problems with my Riv. It's running great, I just have to touch the gas if I'm starting it and it's already warm. Cold start is fine, warm start, it will barely run until I touch the gas. It doesn't bother me too much, but my wife drives it and I need to make it right. Any ideas?

Could you post this with your old thread, so we can see what's been discussed already about your problem?

Have you tested TPS position, IAC function? Have you cleaned the throttle body? Have you tested fuel pressure?

does it start right up when cold, and then take forever and keep cranking when warm until you give it gas? if so, theres a pretty good chance its your crank position sensor. when these fail the car starts normally when cold, but crank forever at operating temp. it could be a fuel issue like deekster said but when a 3800 starts fine in the cold but not when warm that screams crank postion sensor to me.

I read through your old threads, we have the same car with the same developing issues. here's what I've done.
replaced sc bypass valve (you've done this)
replaced all fuel lines
replaced all brake lines
replaced sc coupler

( your symptoms started here on my vehicle)
replaced ALL of the rubber vacuum line connectors under the hood - it's just a time thing, they were all cracked/broken
replaced the LIM and valve cover gaskets.

The rubber connectors and LIM took care of the "won't start warm" problem

I'm currently sitting at 193k miles, the bypass was replaced around 110 and the rubber/LIM was all done around 180k

hope this helps


---oh, and plugs/wires replaced for the wet plug problem. at least check the gaps on the plugs

jonly wrote:

I read through your old threads, we have the same car with the same developing issues. here's what I've done.
replaced sc bypass valve (you've done this)
replaced all fuel lines
replaced all brake lines
replaced sc coupler

( your symptoms started here on my vehicle)
replaced ALL of the rubber vacuum line connectors under the hood - it's just a time thing, they were all cracked/broken
replaced the LIM and valve cover gaskets.

The rubber connectors and LIM took care of the "won't start warm" problem

I'm currently sitting at 193k miles, the bypass was replaced around 110 and the rubber/LIM was all done around 180k

hope this helps


---oh, and plugs/wires replaced for the wet plug problem. at least check the gaps on the plugs

not sure what the brake lines, BBV, or supercharger coupler have to do with the car not starting. also not sure why vacuum would be the problem only when warm, pretty sure a vacuum leak would stand out with a cold engine more. LIM and rocker gaskets could be a problem, but once again not dealing with starting and no difference between hot and cold, those are on going problems. im not sure your plugs/wires fixed your "wet plug problem", that was most likely your leaking LIM.
none of the above have anything to do with a car starting fine when cold, but cranking when warm.
TO OP: scan for codes, if you get any codes having to do with coolant or temp, check coolant temp sensor for faulty wires. if all wires are ok then it could be your coolant temp sensor.
if there are no codes: replace crank position sensor.
dont shotgun parts at your car.

I simply listed everything I'd done in the last year to get my car in drivable condition, and even annotated where the symptoms he was describing started.

the rest of the information was simply information. normal wear on parts on my vehicle which was the same age as the OPs. sorry if I confused you.

OP - Do you have any foam under the oil cap, or oil under your radiator cap? Or do you ever have to add coolant or oil? How often and how much?

I have a very similar issue with starting. For me, I wouldn't say its absolutely always problematic when warm and never when cold but it happens about 2/3 of my startups and even when I don't have to hit the gas, it is never a clean, confident start, like it used to be. I've had this issue for about a year.

I've done a LOT of testing, trial, combing for problems.
The only thing mentioned that I haven't really addressed is the crank sensor. I haven't replaced mine and I have a 97 with 192k on it. I suppose that would definitely be a good thing to try. (not looking forward to pulling the balancer again though...)

There's nothing I can scan for or test to check this before I replace is there? I'm going to check my FSM but if anyone knows any trick.

Problem with the crank sensor is that when they go bad they usually will not set a code. Yes there is a 'no signal' code for the crank sensor *but* the sensor signal is read early enough in the start sequence so that if it's bad, you don't get far enough into startup to be setting codes.

Typical problem is the sensor becomes bad warm. Works when cold and fails intermittently when warm, usually when heat-soaked from the engine.

So during startup with no signal from the crank, the PCM won't turn on the injectors.

Another thing to watch out for however is if the ignition switch is going bad. That will also give you an intermittent no-start because of the sheer number of switched wires going thru the ignition and their different roles in the car.

Albertj

jonly wrote:

I simply listed everything I'd done in the last year to get my car in drivable condition, and even annotated where the symptoms he was describing started.

the rest of the information was simply information. normal wear on parts on my vehicle which was the same age as the OPs. sorry if I confused you.

ok, gotcha

turtleman wrote:

I have a very similar issue with starting. For me, I wouldn't say its absolutely always problematic when warm and never when cold but it happens about 2/3 of my startups and even when I don't have to hit the gas, it is never a clean, confident start, like it used to be. I've had this issue for about a year.

I've done a LOT of testing, trial, combing for problems.
The only thing mentioned that I haven't really addressed is the crank sensor. I haven't replaced mine and I have a 97 with 192k on it. I suppose that would definitely be a good thing to try. (not looking forward to pulling the balancer again though...)

There's nothing I can scan for or test to check this before I replace is there? I'm going to check my FSM but if anyone knows any trick.

i remember hearing one of your exhaust vids and wondering about that, i would definitely say that the CPS is your problem. unfortunately there is no way to test it because as you already know its behind the balancer. like albertj said when this happens you usually wont get a code, which is why i usually go by the cold start=OK/warm start=cranking for longer.
so far its always turned out to be the CPS in that case.
the only time ive ever been wrong at first about this, is a guy on regalgs was having the same issues, but with the p0118 code, it ended up being a broken coolant temp sensor wire but if theres no codes and just a long warm start, CPS it is.

Keep in mind we've seen a few CPS issues that have come down to a break in the wire, not the sensor itself. So check continuity of the wire before you replace the sensor.

SupersportSteve needs to find those pics of the broken wire at the firewall connector and check his for any cracked insulation and partially broken wires. I don't know where that photo is. Maybe under CPS.?

The turtleman recently replaced his whole engine compartment harness from the firewall forward and inspected all connectors, so for him it's probably the sensor that's bad.

This link is Titled Camshaft Sensor, but on page 10 it has a wiring diagram of the crankshaft position sensor and a photo of the firewall plug, where a lot of the wiring problems are popping up.
https://rivperformance.editboard.com/series-ii-engine-transmission-f4/p0341-camshaft-position-sensor-cam-sensor-timing-chain-t4703.htm?highlight=crankshaft+position+sensor

Ok it starts as soon as the gas pedal is pressed some, please connect me how a missing or weak CKP signal will correct itself when the gas pedal is pressed.

Sounds more like corroded wires on the CTS or a "in range" failure, unplug and inspect for green corrosion, a scan will quickly show this.

How about inspecting/cleaning the IAC just for the heck of it if nothing else is found.

All ideas here are easier then pulling the balancer . Just trying to keep it simple.

98inSFl wrote:

Ok it starts as soon as the gas pedal is pressed some, please connect me how a missing or weak CKP signal will correct itself when the gas pedal is pressed.

Sounds more like corroded wires on the CTS or a "in range" failure, unplug and inspect for green corrosion, a scan will quickly show this.

How about inspecting/cleaning the IAC just for the heck of it if nothing else is found.

All ideas here are easier then pulling the balancer . Just trying to keep it simple.

This makes a lot of sense; missing or weak CKP signal does not care whatsoever if the gas is pressed. Gas being pressed would merely be coincidental to getting a signal from a crank sensor that was tickled enough (by starting vibrations) to work, or some other intermittent connection.

Albertj

BUT a bad CKP would also pose other problems, like no start rather then hard start, it is a transistor encased in epoxy, no vibration will affect it, just heat if its bad.
All I am saying is its not the first thing I grab and change..

When I made the post above i was reading more into turtles problem and not the original OP.
My Bad, I should have read back to the beginning of the post more closely and addressed his issue - your correct about throttle position having nothing to do with CKP problems.
I think Derek's post post, the second post on this thread, more correctly asks the questions that need to be answered first.

98inSFl wrote:

BUT a bad CKP would also pose other problems, like no start rather then hard start, it is a transistor encased in epoxy, no vibration will affect it, just heat if its bad.
All I am saying is its not the first thing I grab and change..

and I am agreeing.

technically CKP is a hall effect sensor; they are very similar to transistors, and are typically made from semiconductor materials such as silicon and germanium. They work by measuring voltage across two of their faces when you place them in or pass them thru a magnetic field. Some Hall sensors are fabricated into chips that include other control circuitry (for instance, to activate a switching transistor).

A typical sensor includes an on-chip Hall voltage (meaning Small Voltage)generator that does the magnetic sensing, a comparator to amplify the Hall voltage, an electronic trigger to provide switching delay (technically, switching hysteresis) for noise rejection, and open-collector output. One such package, the US1881, includes an internal regulator to keep the supply voltage constant across a normal (think somewhat sub-freezing to boiling) temperature range.

Depending on how they are packaged/manufactured vibration could be an issue, however you are right, usually the issue is that over time they change behavior when heated such that they no longer sense and/or signal--and given the failure pattern there are other things to look for first. As for crank sensor failure, on our Rivs and thinking about other RivPerformance posts, that failure point can be reached often but not always between 70,000 and 170,000 miles.

Back to your point - yes please check simpler stuff first before pulling the balancer. Pulling the balancer is not like pulling the heads, but it's still true that if only for preventive maintenance and peace of mind, not to mention that the failure pattern suggests other things besides the crank sensor, checking the simpler stuff first is the right approach.

Albertj

deekster_caddy wrote:

OP - Do you have any foam under the oil cap, or oil under your radiator cap? Or do you ever have to add coolant or oil? How often and how much?

I've had just a trace of milky liquid under the oil cap for about 2 years, it never amounts to much. Never had any under the radiator cap. I used to go through some anti freeze, but after replacing the radiator and the water pump and switching to normal anti freeze (about 6 months ago), I've only had to add coolant once.

I appreciate all of the replies, you've definitely given me some things to look for. I'm going to start with checking the wiring and getting together with a friend who has a scanner. I'll keep you posted.

SupersportSteve wrote:

deekster_caddy wrote:

OP - Do you have any foam under the oil cap, or oil under your radiator cap? Or do you ever have to add coolant or oil? How often and how much?

I've had just a trace of milky liquid under the oil cap for about 2 years, it never amounts to much. Never had any under the radiator cap. I used to go through some anti freeze, but after replacing the radiator and the water pump and switching to normal anti freeze (about 6 months ago), I've only had to add coolant once.

Sounds like you may be losing coolant from the LIM gaskets, if there is none on the ground. You should never have to add coolant, unless there is a leak. Based on the last 3 3800 LIM gaskets I've done, plus other pictures I've seen, I would say if they've never been done they should be on ALL 3800s that had plastic OE LIM gaskets. It may or may not solve your problem, but I can almost guarantee they need replacing. Get the GM gaskets, they have revised them to be aluminum, Fel Pro still gives you plastic gaskets.

deekster_caddy wrote:

Get the GM gaskets, they have revised them to be aluminum, Fel Pro still gives you plastic gaskets.

Felpro has aluminum ones now

turtleman wrote:

deekster_caddy wrote:

Get the GM gaskets, they have revised them to be aluminum, Fel Pro still gives you plastic gaskets.

Felpro has aluminum ones now

I heard recently that Fel-Pro upgraded all their 3800 LIM gaskets to aluminum so you don't have order for a 2004 GTP or from GM anymore.

SupersportSteve, what say you.???

I'll agree, it probably does need LIM gaskets. But is that what's causing my problem? I'm rather not do them until it get's a little warmer around here, and I don't quite understand how it would cause the problems I'm having.

Steve,
I've gone back to the second post made on this thread.
You should start with the easiest things that won't cost much money, just time.
These need to be ruled out as potential problems before you start thinking about replacing LIM gaskets anyway.
This thread kind of ran away on you. Basics first.

deekster_caddy wrote:

Could you post this with your old thread, so we can see what's been discussed already about your problem?

Have you tested TPS position, IAC function? Have you cleaned the throttle body? Have you tested fuel pressure?

You can get a can of Throttle Body Cleaner and MAF Cleaner from the auto parts store to start by cleaning things up, if it hasn't been done in a while, it's due. You can use a used toothbrush carefully to help you clean the MAF if the wires are excessively dirty and use it in the throttle body as well. I save used toothbrushes just for this kind of work. Be careful with the MAF though.
Remove the MAF for a good cleaning and be very careful with the handling the wire screen as it measures air flow and is relatively delicate.
After having removed the MAF you now have much better access to the throttle body and can clean that properly.
Remove the IAC and clean the pintle and look for excessive carbon or varnish builup that could be causing it to stick or operate erratically. Test the IAC for proper operation electrically per the FSM.
Test fuel pressure at idle and with engine off and key on. Report back with results. Your looking for around 40 - 50 psi at idle IIRC. Again the FSM will tell you exactly what you should be getting. Look for any needle bouncing or erratic movement. Should be a steady reading. The gauge should also hold the pressure after the car is shut off. Watch it for a while and see if it bleeds down. This is important info also.
Replace your air filter with new, when your done with the rest of the intake cleaning, if it hasn't been done recently.
Start with cleaning and testing these things first. BTW, DO NOT USE Carb Cleaner to clean your MAF, it will ruin it. Use the correct products.

Steve, one other thing I wanted to ask you to try doing before any of the above cleaning and testing and that is:
When you get in the car with a WARM engine, prior to trying to start it, will you turn key to the "ON" position (not start position) and leave it in the ON position for a few seconds before turning it all the way to Start and see if that helps with the problem.
Let us know what you find on that test. If car start's good that way then you need to move on to the "Fuel Pressure Test" with a test gauge at the fuel manifold as mentioned above.
Good Luck and report back with your findings and any questions. I hope you have the FSM for your year car, it sure would be helpful for these kinds of issues.
If you don't we'll try to describe what to do, but sometimes troubleshooting problems can be hard without the books. We'll see.
Cheers.

Thanks Rick, you've given me a good place to start. I haven't cleaned the MAF or the throttle body. I do have MAF sensor cleaner and a used toothbrush, it does have a new air filter and fuel filter.