1999 GMC Sonoma misifing BADLY; 2.2 Liter 4 cyl

Blaine B. · 11-18-2009, 05:04 AM

A friend of mine recently purchased a 1999 GMC Sonoma (2 wheel drive and 2.2 liter 4 banger with automatic transmission) from a local auction. Advertised as driving and running, although we later found out that is a bit deceptive as it says it does not have to be road safe or road legal to be considered as driving and running. Anyway besides all that and nothing to do except keep it now, the original idea was to fix a few small things, add a radio, and resell it for profit...bla bla bla

Anyway the truck was misfiring badly when he first started it at the auction location. Suspected the cat was clogged, so cut it off....no change, just 10x louder. So he had it towed back to my place. I pulled all of the plugs. They turned out to be Bosch Platinum +2's. Cylinder 1 and 2's plugs appeared to be in a lean environment. The plugs from cylinder's 3 and 4 appared to be in a rich environment and covered with soot. So I cleaned the 4 plugs with a wire brush and reinstalled. Also made sure the "gap" of the two grounds on each plug were even, as some appered to be slightly closer to the electrode than others. The metal on these grounds seems to be softer and thinner compared to any other spark plug I've seen.....

Anyway I ran a resistance check on the 4 plug wires too. Three gave readings, one gave absoultely NO reading at all. Thought there was an internal brake in the wire. So we installed a new set of plug wires without any change.

Tonight I welded the cat back onto the rest of the exhaust and he replaced both of the coil packs with new units. No change.

Motor appears to be misfiring really badly. The motor is moving around inches in each direction. It has no power at all. Also if you turn the lights on, they fluctuate in brightness. Just to show how bad the "misfire" is (if it is truly a misfire or not) if it is causing the alternator to charge at an inconsistent rate.

There does not appear to be any coolant in the oil or vise versa either.

Actually today after the new coil plugs were installed, it would not start without putting the accelerator pedal to the floor (so that the injectors are disabled during starting)

Also you can smell A LOT of gas when starting the vehicle or when it is running.

Perhaps the injectors are screwed up? If this were the case it is probably more than 1. I think the intake manifold would have to come off to get to these. This small 4 banger is really packed in there......nasty!

Whoever had (or worked on) this truck prior was really a dumbass. The wire that is supposed to hook up to the A/C compressor clutch was left dangling and got chewed up by the radiator fan while the plug which was intended to plug into the intake air temp sensor (in the air intake tube) was jammed into the A/C plug. They are clearly different plugs too, not even identicle!

The "service engine soon" light is also on. We are working on getting a code reader to read the codes. I am guessing it will show a bunch of misfire codes and that is it.

Does anybody have any GM experience or any suggestions relating to these problems?

Thanks in advance!

Blaine B. · 11-18-2009, 11:03 PM

Got another buddy to come by today with his code reader. Only code it was throwing was an "injector circuit open" code or something to that effect.

Ohmed the injectors themselves. Two of them were reading 2.1 ohms and two of them were reading 2.2 ohms.

Also checked the plugs to each injector. 3 of them were reading .1 volts while one of them was reading .8 volts (WHILE CRANKING THE MOTOR OVER)

What voltage are the injectors supposed to be receiving? I am thinking that .1 volts is way too low....

cmarenger17 · 12-01-2009, 11:02 PM

Ive had a 2.2L sonoma for years and it was a good engine if your not in a hurry to get anywhere fast. But as far as your problems go Id start with a fuel pressure test, GM pumps are always going. or the fuel pressure regulator. If your the pump is weak than you will be getting some mean misfires. AS far as testing your injectors I dont think your multimeter will be able to pick up the readings, they pulse very quickly, in the millisesonds and are controlled by the PCM. Youd have to hook it up to a lab scope in order to get a accurate reading, any shop with one can do it. if your fuel pressure is good and regulator is working. Your injectoor resistance seem fine according to gm spec, and if they are reading all the same its unlikely they are all reading bad..Usually if you could get a stethoscope on each injector you could listen to see if they are workig properly but theres no way your getting it on the injectors with the intake on..Next Id test your egr, if yours has it. Mine did but it was a 94. With the egr stuck open it will run very rough, My old 4.3l did and it didnt even set a code, took many nights in the garage before i got it fixed.. The PCM is usually the last step but Id look at everything first.Check your grounds/fuses/relays too.hope this helps.

Blaine B. · 12-02-2009, 02:32 AM

Any ideas about the 98 Malibu working in the Sonoma or is it a no-no? carpart.com lists a bunch of Malibu PCM's being compatible with the Sonoma and the 2.2L, including PCM's from Cavelier's and Sunfire's too.

myjeepsbigger · 12-03-2009, 12:26 PM

What was the actual code number?

11-18-2009, 05:04 AM	#1
Blaine B. Trail Guide Join Date: Nov 2005 Location: Northwest Indiana Posts: 1,986	1999 GMC Sonoma misifing BADLY; 2.2 Liter 4 cyl A friend of mine recently purchased a 1999 GMC Sonoma (2 wheel drive and 2.2 liter 4 banger with automatic transmission) from a local auction. Advertised as driving and running, although we later found out that is a bit deceptive as it says it does not have to be road safe or road legal to be considered as driving and running. Anyway besides all that and nothing to do except keep it now, the original idea was to fix a few small things, add a radio, and resell it for profit...bla bla bla Anyway the truck was misfiring badly when he first started it at the auction location. Suspected the cat was clogged, so cut it off....no change, just 10x louder. So he had it towed back to my place. I pulled all of the plugs. They turned out to be Bosch Platinum +2's. Cylinder 1 and 2's plugs appeared to be in a lean environment. The plugs from cylinder's 3 and 4 appared to be in a rich environment and covered with soot. So I cleaned the 4 plugs with a wire brush and reinstalled. Also made sure the "gap" of the two grounds on each plug were even, as some appered to be slightly closer to the electrode than others. The metal on these grounds seems to be softer and thinner compared to any other spark plug I've seen..... Anyway I ran a resistance check on the 4 plug wires too. Three gave readings, one gave absoultely NO reading at all. Thought there was an internal brake in the wire. So we installed a new set of plug wires without any change. Tonight I welded the cat back onto the rest of the exhaust and he replaced both of the coil packs with new units. No change. Motor appears to be misfiring really badly. The motor is moving around inches in each direction. It has no power at all. Also if you turn the lights on, they fluctuate in brightness. Just to show how bad the "misfire" is (if it is truly a misfire or not) if it is causing the alternator to charge at an inconsistent rate. There does not appear to be any coolant in the oil or vise versa either. Actually today after the new coil plugs were installed, it would not start without putting the accelerator pedal to the floor (so that the injectors are disabled during starting) Also you can smell A LOT of gas when starting the vehicle or when it is running. Perhaps the injectors are screwed up? If this were the case it is probably more than 1. I think the intake manifold would have to come off to get to these. This small 4 banger is really packed in there......nasty! Whoever had (or worked on) this truck prior was really a dumbass. The wire that is supposed to hook up to the A/C compressor clutch was left dangling and got chewed up by the radiator fan while the plug which was intended to plug into the intake air temp sensor (in the air intake tube) was jammed into the A/C plug. They are clearly different plugs too, not even identicle! The "service engine soon" light is also on. We are working on getting a code reader to read the codes. I am guessing it will show a bunch of misfire codes and that is it. Does anybody have any GM experience or any suggestions relating to these problems? Thanks in advance! __________________ 1995 Cherokee Country L-6 4.0 H.0. / AW4 / NP231 / D30 / C8.25 Mix & Match 7" suspension lift, TNT Boomerangs w/ RE spacers, GoFerIt OTK, Rusty's Tierod Conversion, Rusty's CA's & TB, Electric Fans, Soft 8's, RC drp bckts, AA SYE w/ TW DS, JKS disco's, fuel skid, stainless lines, & 33x12.50 BFG MT's

11-18-2009, 11:03 PM	#2
Blaine B. Trail Guide Join Date: Nov 2005 Location: Northwest Indiana Posts: 1,986	Got another buddy to come by today with his code reader. Only code it was throwing was an "injector circuit open" code or something to that effect. Ohmed the injectors themselves. Two of them were reading 2.1 ohms and two of them were reading 2.2 ohms. Also checked the plugs to each injector. 3 of them were reading .1 volts while one of them was reading .8 volts (WHILE CRANKING THE MOTOR OVER) What voltage are the injectors supposed to be receiving? I am thinking that .1 volts is way too low.... __________________ 1995 Cherokee Country L-6 4.0 H.0. / AW4 / NP231 / D30 / C8.25 Mix & Match 7" suspension lift, TNT Boomerangs w/ RE spacers, GoFerIt OTK, Rusty's Tierod Conversion, Rusty's CA's & TB, Electric Fans, Soft 8's, RC drp bckts, AA SYE w/ TW DS, JKS disco's, fuel skid, stainless lines, & 33x12.50 BFG MT's

12-01-2009, 11:02 PM	#3
cmarenger17 Newbie Join Date: Nov 2009 Posts: 5	Ive had a 2.2L sonoma for years and it was a good engine if your not in a hurry to get anywhere fast. But as far as your problems go Id start with a fuel pressure test, GM pumps are always going. or the fuel pressure regulator. If your the pump is weak than you will be getting some mean misfires. AS far as testing your injectors I dont think your multimeter will be able to pick up the readings, they pulse very quickly, in the millisesonds and are controlled by the PCM. Youd have to hook it up to a lab scope in order to get a accurate reading, any shop with one can do it. if your fuel pressure is good and regulator is working. Your injectoor resistance seem fine according to gm spec, and if they are reading all the same its unlikely they are all reading bad..Usually if you could get a stethoscope on each injector you could listen to see if they are workig properly but theres no way your getting it on the injectors with the intake on..Next Id test your egr, if yours has it. Mine did but it was a 94. With the egr stuck open it will run very rough, My old 4.3l did and it didnt even set a code, took many nights in the garage before i got it fixed.. The PCM is usually the last step but Id look at everything first.Check your grounds/fuses/relays too.hope this helps. Last edited by cmarenger17; 12-01-2009 at 11:47 PM.

12-02-2009, 02:32 AM	#4
Blaine B. Trail Guide Join Date: Nov 2005 Location: Northwest Indiana Posts: 1,986	Any ideas about the 98 Malibu working in the Sonoma or is it a no-no? carpart.com lists a bunch of Malibu PCM's being compatible with the Sonoma and the 2.2L, including PCM's from Cavelier's and Sunfire's too. __________________ 1995 Cherokee Country L-6 4.0 H.0. / AW4 / NP231 / D30 / C8.25 Mix & Match 7" suspension lift, TNT Boomerangs w/ RE spacers, GoFerIt OTK, Rusty's Tierod Conversion, Rusty's CA's & TB, Electric Fans, Soft 8's, RC drp bckts, AA SYE w/ TW DS, JKS disco's, fuel skid, stainless lines, & 33x12.50 BFG MT's

12-03-2009, 12:26 PM	#5
myjeepsbigger ~ Jitterbug ~ Join Date: Feb 2003 Location: MyJeepsLand, IL Posts: 6,353	What was the actual code number? __________________ Live now, Pay later.