Rough erratic idle, hesitation, stalling, sulpher smell

[JIMMY92w]

I have a 1992 GMC Jimmy, 4.3L v6 (high Performance) V.I.N (w) with 97,000 Kms. Recently she emitted a strong sulpher smell that only lasted briefly, about the same time the engine was sounding deep & growling. After the smell she immediately started to rough idle and idle erratically. When proceeding to put her in gear she almost stalls, hesitates, and then she suddenly starts to move. At this time these problems were only noticeable when idling, initial accelerating, and decelerating. After the engine started to rev up past the 1000rpm all seemed normal, even though the Service Engine Soon light turned on. When slowing down for a stop the engine wants to stall, and power steering and breaks want to lock up. If she stalls the only way to start her is to put the gas to the floor and turn the key. When she starts you need to work the gas to keep the idle at 700rpm+ or else she will stall.

Over the last 3 years, maybe 3 times in total, I remember smelling sulpher and each time I did the car wanted to stall out and idle rough. If it did stall you needed to floor her while turning her over to start. But these three incidences cleared up pretty quickly and the car resumed operating at her normal state.

I’ve been reading this form (Jimmy & Blazer) and have ideas but no improvements have been made. One thing that has changed is she is slightly surging at idle and when driving on the road.

Last week (3 days before the problems started) I changed the plugs with NGK G-power (NGK platinum plug) and went on a 600KM drive and everything went very smoothly. I pulled them out last night and they looked fine except they looked a little wet like oil or gas, so I cleaned & reinstalled.

Also replaced was the oil, oil filter, air filter, (before problem) gas filter, distributor cap and rotor (After problem).

I want to change the O2 sensor but I need to find one first! Also I can’t find the MAF & EGR valve. Where are these located? If I pull of the intake manifold do I need reinstall with a new gasket? If the Cat is clogged do I also need to replace the CPI? I pulled of the round valve under the plastic plate on the intake and the insides do not look washed.
If I put my hand over the exhaust pipe a ‘regular’ flow of exhaust is felt.

I put some Motor Master Fuel Injector cleaner and some methyl hydrate in the fuel tank.

I have an appointment to get ripped off at the dealership this Monday; I’m hoping that this down time will give me a chance to get her back to normal.

Any help would be greatly appreciated.

[Jaysue]

Sounds like your Catalytic Convert needs to be replaced. The exhaust is not flowing properly, backed up. I would have it checked.

[jsgold]

These engines have a tendancy to leak gas in the plenum, and can put fuel into your oil as well. The injectors on the CPI are prone to sticking and if this is the case it is a very expensive job for a dealer to do. Parts alone can set you back 400-500 dollars from a dealer if this is the case. In bad cases the fuel can even fill up a cylinder and cause lock up. The extra fuel burning will take out your converter also. Check the forum for CPI problems and spider injection problems. Look in the Blazer forum and S-10 forum as well as many use the 4.3 CPI "W" motors. There are 2-3 folks in these that have worked on these a lot. Might want to check your oil for gas smell since you stated the plugs were possibly wet. Hopefully this is not the case, but be prepared if it is.

PS - The EGR is on the very front of your engine, and a bit cramped for space. Look between the radiator and front of engine. Your engine should not have a MAF , rather it should have a MAP sensor. And yes, the EGR's tend to get clogged often. Best to clean it asap.

[JIMMY92w]

The Exhaust appears to be coming out at a normal rate, but what is normal exhaust flow? I picked up a scanner and extracted codes 12 & 32. Code #32 in a fuel-injected system points to the EGR valve. I’m still having trouble locating it. Is it located below the Serpentine drive belt tensioner? Alright I found it. I take that it is alright to clean a Linear ERG valve??

Also, I was driving on the highway after I scanned it and it started running a lot better. It will idle, barely hesitate, and will not almost stall when slowing down. I gave it gas and had it up to 140 KMH, and it seemed really smooth with lots of power. I’m wondering if a chunk of carbon was lodged in the ERG and it got sucked in.

Well back to the Garage I go…

[BlazerLT]

You need to do these two things.

1.) Remove the EGR valve and remove any carbon blocking the pintle open and clean it thoroughly with TB cleaner and a toothbrush and scub out the carbon.

2.) Remove the top votec name place and remove the round valve under it noting its orientation for reinstallation.

Take a flashlight and look down into the plenum and look for golden washed spots where leaking fuel has washed the black grime that should be in there. Smell for excess fuel and check your oil and see if it is overfilled which could mean a mass leak of gas going into the oil. Smell the oil dipstick for gas.

Idle problems are usually because of the EGR valve needing cleaning and reinstalled with a new EGR gasket.

Injector/nut kit leaking will usually be the problem when the engine will not star up and will require extra cranking to get the motor started after sitting overnight etc....

[94 Jimmy]

When did you change the O2 sensor last? If its been over 50K Mi, that might be something to try. The sulfur, rotton eggs, burned hair, etc. smells are from a mixture that's too rich. This can be caused by a leak in the intake system or an O2 sensor thats gone out of calibration. If the cheap fixes don't work try the sensor, it'll cost you $50 but it cures a lot of problems
Good Luck, let us know what you find.
94

[JIMMY92w]

Ever since she started running better from that rip on the highway, the performance has not declined. I did pull of the EGR valve and clean it up, and there was evidence that it could have been possible fouled by carbon. I reinstalled with a new gasket. Also I did install a new O2 sensor, even though the original O2 sensor looked clean.

These two fixes had no noticeable impact on performance, and she’s still running how she should.

I looked into the plenum and the entire inners appear to be a golden black. Maybe it’s not totally black because the engine has less than 60,000 miles? I can see what looks like carbon slowly coating the plenum! What would happen in the plenum if the engine flooded with gas?

Also, if one wanted to remove the EGR valve and install a block off plate, other then disconnecting the connector from the EGR would anything else need to be preformed so not to confuse the computer?

[BlazerLT]

Originally Posted by JIMMY92w

Ever since she started running better from that rip on the highway, the performance has not declined. I did pull of the EGR valve and clean it up, and there was evidence that it could have been possible fouled by carbon. I reinstalled with a new gasket. Also I did install a new O2 sensor, even though the original O2 sensor looked clean.

These two fixes had no noticeable impact on performance, and she’s still running how she should.

I looked into the plenum and the entire inners appear to be a golden black. Maybe it’s not totally black because the engine has less than 60,000 miles? I can see what looks like carbon slowly coating the plenum! What would happen in the plenum if the engine flooded with gas?

Also, if one wanted to remove the EGR valve and install a block off plate, other then disconnecting the connector from the EGR would anything else need to be preformed so not to confuse the computer?

Don't start blocking off the egr. Will cause detonation and performance loss.

Also, reset you computer when you clean or replace any of the sensors.