Sputters, stalls and backfires oh my.

[FreeUlster]

My 91 started to sputter and stall and backfire. It started gradually but now I get 7 miles to the gallon and she runs ugly. I put new plugs and coil pack over a year ago into it and it ran well. Now she stalls when making turns or won't start. I go maybe 90-100 miles on a full tank. She will back fire when giving her gas when going up hill. Back fires when starting. Sputters when accelerating on flat highways. My vacum lines are connected to the tower on the engine. Please help I miss driving my truck.

 

[ExplorerDMB]

have you replaced the fuel filter recently? Check your fuel pressure.

-Drew

 

[FreeUlster]

I havn't done anything with the fuel filter and now feel kinda stupit. Now that I have establised that i am stupit, how do you check fuel pressure?

 

[MrShorty]

In the stickies at the top of this forum is Glacier's "Fuel pressure mini diary." Reference that.

 

[FreeUlster]

Thanx.

 

[FreeUlster]

--------------------------------------------------------------------------------

I have a 91 auto. I replaced the coil pack, plugs, and wires. This thing stalls when I put it in drive or reverse. It idles fine in park or neutral. No sucking sound indicating a vacume leak and the tubes are all connected to the manifold tree. I am at a loss and need this thing to get to work this weekend(expecting a snow storm). I am not getting a CEL and yes the bulb is good. I need any help I can get.

 

[MrShorty]

What did you get from your fuel pressure test?

Just because the CEL isn't on doesn't mean you can't pull codes. I would suggest pulling codes as well (see my "notes on pulling EEC-IV codes" in the EEC-IV forum).

 

[MrShorty]

This thing stalls when I put it in drive or reverse. It idles fine in park or neutral.

Another thought. Based on this little piece, can you better describe the "stall?" It's not common, but not unheard of for the torque converter lockup clutch to get stuck engaged, which will result in symptoms like this. The engine won't usually "sputter" and die in this case, however. It will usually idle fine, then just die when put in gear (much like popping the clutch on a manual transmission at idle).

 

[FreeUlster]

yeah, thats what it does. I just dies when put into reverse and mostly when in drive. When it does engage drive it sputters. Put it in neutral and she purrs like a kitten.

 

[FreeUlster]

I bought a reader at wally world. I had a stored code for intake air temp out of range and PIP malfunction. I cleared the codes, and drove around for a while then rechecked KOEO and KOER and had all passes. CAr ran good this morning but with a puttering noise. let it sit for several hours. Now it is hard to sttart and stalls. It stall when reverse is engaged, when idleing at a light or when the rpm dips under 800-1000. This is driving me ape s%!t. Other than that I ran sea foam a few weeks ago. Could it be a blocked Cat or ruined O2 sensors?

 

[MrShorty]

Has the PIP code continued to stay away? PIP signal is critical to the operation of the engine, and if it's intermittent, you will get intermittent operation and stalling. Even if the PIP code hasn't come back, I would probably take the time to verify for certain that the ICM doesn't have an intermittent power supply, or ground, or that the wiring from the CKP to the ICM has an intermittent break.

If you haven't followed savegefan's story (see EEC-IV forum), he found his problem was a loose connection near/in the ignition switch.

 

[FreeUlster]

In the event I have a bad ICM would a hypertech chip or equiv. be a solution to replace the ICM? or are they seperate.

 

[Runnin'OnEmpty]

FreeUlster, forget about a chip for now, it won't help the problem.

I think you have more than one trouble. Since you don't have a current code showing, you'll have to eliminate some things. First check the fuel pressure, and pull the vacuum hose off the regulator to check for raw fuel inside.

Easiest way to check for a clogged cat converter is with a vacuum gauge. You'll get very low and erratic vacuum if it's clogged.

Next check the TPS output with a multimeter. Do a search, there's lots of writeups on how to check it. Basically you're looking for a smooth voltage transition when the throttle is advanced.

Lastly, it might be a faulty NSS (neutral safety switch). Some of these puppies can be taken apart, cleaned and lubed to restore serviceability. Again, do a search for info.

Just some things to check, good luck,
ROE

 

[Runnin'OnEmpty]

Oops, double post. Can't delete.

 

[FreeUlster]

Thanx for your advice. I suspect the pcm is faulty which seems common on the earlies, but I will check the other areas you've suggested.. I'm wondering, do you think it's possible that the sea foam I ran caused the carbon in the engine to collect in the cat and clog it?
BTW I did another code check today and I got #14 as a stored code on KOEO, otherwised all else passed as well as KOER all passed. Is a replacement PCM the solution for a code 14? :exp:

 

[Runnin'OnEmpty]

OK, now we're getting somewhere. Code 14 is "ECA has detected intermittent loss of profile ignition pickup signal/PIP during recent operation."

As you and MrShorty discussed previously, I think the ICM is suspect. How does the tach read when the engine stumbles? If it goes to 0, that would confirm a bad ICM.

 

[savagefan]

No, it just means PIP fault. Many things can cause this, mine was a bad ignition switch. Lost power to ICM no PIP out, simple, bugger tracking it down. Before you start buying parts do some diagnostics and save your hair. You can eliminate most of your sensors as culprit by seeing how it behaves cold after codes cleared, open loop, sensors are not a factor. Sounds like a TC prob to me, but good luck.

 

[FreeUlster]

I put a new ICM in it and it does run much better, I cleared the codes and drove it for a few days. I still have poor gas milage and stalled once(tach dropped below 500 then hit zero and died). I only made 52 miles on a half tank of gas. The engine lopes a bit and makes me think I have a clogged cat. My only mods a a true rev induction, flowmaster cat back and james duff 3inch lift. I replaced my MAF about 2 years ago and icm two days ago. I ran sea foam(bottle and deep creep spray). I checked codes again and am getting 14 which I had before and now I picked up a 66 maf voltage low which is a new one for me. The KOER was all normal. I want to run a cylinder diagnostic after the KOER but I cant until the KOEO codes are resolved. You mention a TC issue I had my trans rebuilt and a new tourqe converter put in about 4 or 5 years ago. The stalling when put into reverse is gone since I replaced the ICM(as well as the knocking and backfiring) and the last stall was slow coasting up a hill at my kids school(15mph) Any help would be appreciated

 

[MrShorty]

So the CM 14 continues to come back? Is the 66 a KOEO or CM code (would guess CM because you say you got a pass code from the KOER test)? Have you verified that you don't have an intermittent break in the ICM power, ground, or in the CKP wires?

Just so you know, your '91 4.0 is batch fired fuel injection, not sequential fuel injection. Only SFI models can perform a cylinder balance test after the KOER test. If you want to do a cylinder balance test, you'll have to do it manually.

 

[FreeUlster]

Thanx MrShorty. To be honest the wiring under there is a nightmare to follow and I was hoping the ICM would solve this but now I am getting a MAF low volt code as well as the code 14. Both codes are CM. I followed the wiring from the MAF to a bundle that seems to run under my battery tray. The black tubing the wires run in is broken open from rubbing the tray but it was getting to dark to see if any wires are abraided. I have no problems splicing, soldering etc. (I rewired my 64 corvair but there is a lot more room to work with in a vair). Also I still haven't changed sparkplug wires 1 and 3 ( I still suffer from post traumatic stress from doing the plug change a while back) If they are bad perhaps they could be causing some of my problems?