P0141

Mine leaks externally a bit from the corner. I noticed it leaks more in the cold weather. Nothing alarming, and my engine runs great. I know I'll have to do this job sooner or later.

Well, I pulled the intake. The gaskets had turned into mush. I am amazed the thing ran at all!

Thank you all.

Mikel wrote:

Well, I pulled the intake. The gaskets had turned into mush. I am amazed the thing ran at all!

Thank you all.

Have fun replacing it!

Nice call, Larry!

AA wrote:

Nice call, Larry!

Ouch!

Hello,
My L-67 saga isn’t quite over. I replaced the intake gaskets and the engine still doesn’t run well. Besides burning about 30% more fuel than before and still having nowhere near its original power, at anything over slight throttle, it will have a continuous high frequency miss (a sort of R-R-R-R-R-R-R-R-R-R-R). I still get a P0300 error code (random misfire).

I checked engine vacuum again and I get a steady 20-21 inches at idle, so my intake gaskets were certainly bad. I initially thought I may have damaged an injector o-ring: I sprayed starting fluid all over the engine at idle and it didn’t have any effect on the idle.

I connected an OBD2 reader and something puzzles me: The engine is generating at least 20” of mercury at idle, but the MAP sensor is only reading 10-12”. The rubber boots in that sensor’s line look OK, so I don’t think I have a vacuum leak there. Could I have a bad MAP sensor?

Thank you.

I would check all the plastic lines and rubber fittings that go to/from the MAP sensor before you replace it. One of the plastic lines may have a kink in it, or a little crack. Same thing goes for all the rubbers. Those lines attached go from the MAP sensor all the way to the LIM fitting under the snout of the S/C, and then to the Fuel Pressure Regulator and the Boost Solenoid. They're all connected. Your vacuum gauge might be reading proper vacuum on the engine side, but not at the sensors. This would absolutely cause drivability concerns.

Or, the MAP is being stupid and needs to be replaced. It's hard to check a MAP sensor. You'd need a table that lists BARO and in/Hg to compare. You'd have to disconnect the MAP sensor vacuum lines and apply a set amount of vacuum with a vacuum pump to the sensor itself. While doing this, you'd have to monitor the reading on the scan tool to see what the PCM is seeing, then compare it all to the chart. It's really the only way to diagnose a bad MAP if it isn't electrically bad.

Well, it appears the MAP sensor isn't it. I have an extra one and I plugged it in, using a vacuum line to bypass the factory line, in case it was leaking. Nope, it runs exactly the same

Thank you.

A code P0141 may mean that one or more of the following has happened: open or short to ground in the wiring harness O2 heater circuit wiring high resistance O2 heater element resistance is high Internal short or open in the heater element

Read more at: http://www.obd-codes.com/p0141
Copyright © OBD-Codes.com

I think I had that problem and ended up replacing my o2 sensor with a o2 simulator.I believe that fixed my problem check out ZZP site

http://shop.zzperformance.com/store/p/468-O2-Emulator.aspx

chitown_riv98 wrote:

I think I had that problem and ended up replacing my o2 sensor with a o2 simulator.I believe that fixed my problem check out ZZP site

http://shop.zzperformance.com/store/p/468-O2-Emulator.aspx

Mine idles badly from a cold start... Wouldn't the O2 sensor be excluded at that time, with the engine running in open loop?
Thanks.

Hmm. My car ran like crap from the start and the exhaust smelled rich. Could possibly be something else though.

chitown_riv98 wrote:

Hmm. My car ran like crap from the start and the exhaust smelled rich. Could possibly be something else though.

Thanks. But why a O2 sensor simulator and not a new sensor?

The rear O2 sensor won't cause the car to run like poo. It's the front O2 that will cause concerns. The rear O2 does nothing but "monitor" the Catalytic Converter. People who remove the Cat can put a Simulator in place so the SES light doesn't come on. You CANNOT put a Simulator in the front O2's place.

Again, the REAR O2 WILL NOT cause misfires or anything you're experiencing.

What I don't understand is why the O2 sensor would affect cold starts, as - as far as I know- it is not used until it warms up.

In any case, the readings from the scanner at idle for both sensors are:

O2S11 (V): 0.825
O2S12 (V): 0.795

Thank you.

Changed the upstream O2 sensor with a used one I got from a running engine and it made no difference

Out of curiosity, what are the symptoms of a bad supercharger?

When the engine misses at idle, it makes a loud coupler-like noise. No other abnormal noises.

Thanks.

Hello,
I checked engine compression. All cylinders came out at 150PSI, except for one at 120. I added some oil to that one and compression climbed to 125. A valve beginning to burn?

Would this be enough to cause the engine to run terribly? I had a 1997 Cherokee with the 4.0. Burnt valve and 90PSI of compression in one cylinder. It had a slight miss at idle and very slight at low RPMs, but ran beautifully.

I have access to a good running, low mileage engine from a SC 1998 Grand Prix. (mine is a 97)

Other than the engine mounts, there seem to be some differences in the sensors and wiring harness. Any other differences I should be aware of? If my current engine needs a valve job, I'd rather use the other engine.
My current engine came from a junkyard 70,000 miles ago (now has about 200,000), so it was well worth the $500 price and the weekend spent swapping it three years ago. Never burned a drop of oil.

Thanks.

A bad cylinder or a bad valve isn't going to have an intermittent problem. It's either there, or it's not. Hard parts inside the engine don't just simply cure themselves by cycling the Ignition.
I would soon put an Ignition Switch in the car before I go putting an engine in it. The fact that you can get the problem to "fix" itself by cycling the key seriously bothers me. You've damn near rebuilt or replaced everything else. I don't remember, but did you replace the Crank Sensor? Have you checked it? Crank Sensors can cause weird misfire problems too.

Yes, you've fixed a few issues that the car obviously had, but we haven't cured the actual problem yet. At this point, we're all just guessing (we can't actually see what's happening).

Hello,
Perhaps I haven't explained myself properly. Cycling the ignition switch does nothing. The engine does not run well at any time.

 At a cold start, it idles very badly and runs very badly. When the engine warms up, it will run kind of OK at light throttle, but anything past (my estimation) 15% of throttle causes the engine to start missing constantly (the R-R-R-R-R-R I mentioned), but once warm it idles somewhat OK, but with frequent misses.

 Right now, at best I am getting 50% of the power the engine used to make. When cold, nowhere near that. The plugs came out fairly dark, which is consistent with rich smell of the exhaust.

 I haven't replaced the crank sensor yet - I had a bad one in another 97 Riviera and at least in that one, the symptoms were just intermittent misses, no loss of power. And I did get a crank sensor error code, which hasn't happened this time.


Thanks.

Oh Jesus. I'm so sorry. I was thinking of the other post (digi's jerks under load thread) relating to misfires apparently. God dammit I'm an idiot. Again, I apologize.

If a valve/cylinder is bad enough, it'll do exactly as you're describing. I think you might just want to throw a new head on there though instead of a new engine. Do you know anybody that has an air fitting that'll go into the spark plug hole with shop air? If you pull the Valve Covers and the Rockers off, you will literally hear air rushing past the bad valve on that cylinder with air introduced to that cylinder. Right now, you know exactly which one to test. This way, you can get away with actually fixing the problem.

The '98 GP engine will work, but you'll have to strip it of all it's brackets and mounting hardware, and transfer almost EVERYTHING from the Riv to it. Basically, you'll need to strip is down to a bare block.

No problem. You help a lot of people and mix ups are bound to happen

I still have the original engine that came with the car. It had been rebuilt 20,000 miles earlier when it developed a rod knock. The crank journal was badly damaged when it got to me, so I went the junkyard engine route.

But I suspect the heads were rebuilt at the time, and looking at how much stuff needs to be transferred from the other engine, I wonder, if as you say, if I'm better off just swapping heads.

Thanks.

Well, bare block and heads. The engine itself will work no problem, it's just all the mounting brackets, Alternator mounting, tensioners, etc etc that are different.

Seriously though, I would have somebody check the valves on that cylinder before you do anything else. Hopefully it's in the front bank of cylinders. It could be checked within an hour or so if that's the case.....and find somebody that will do it the way I described, not someone that's tells you that you have to take the head off the car. The hose I mentioned looks like a Compression Tester hose, but it has a fitting on it for an air hose. We use them to hold the valves up when we change Valve Springs without removing the head(s). If an exhaust valve is bad, you'll literally hear the air coming out the tail pipe. If an intake valve is bad, you'll hear it through the throttle body. The Rockers MUST be removed in order to check it. If you don't, the pushrods will hold the valves open and you won't get the diagnosis you're looking for.

Got a new problem!

Now when I start the engine, it will idle for about two seconds and it will die. It starts every time.

I don't have a fuel pressure gauge handy, but I opened the Schrader valve in the fuel rail after the engine died and there was almost no pressure (I know how hard it shoots out normally).

Obviously the pump is turning on for a brief period, as the engine starts and idles briefly, so I think that rules out the pump and relay.

Any suggestions?

Thanks.