Hesitation

[F14CRAZY]

Howdy. A couple days ago my '92 XL developed a hesitation. It starts up fine and keeps a constant idle speed but you can see the motor shaking more than usual. From the exhaust it "putts" every second. It started on the way back from Grand Rapids to Lansing (nice high speed, 70 mile trip each way)

When under a medium/heavy load (like acceleration in 3rd or 4th gear (manual tranny) from 1500 rpm, or doing freeway ramp acceleration) it hesitates. It still gets up to speed. It kind of goes away if you get the RPM up (like past 2.5k) but not really

It just suddenly started doing this. I tried a bottle of techron fuel system cleaner and a tank of gas, but I've run that over 100 miles and hasn't cleared up. I disconnected the battery to give the computer a chance to reset but that didn't help any either.

CEL is not turning on

Air filter is clean, spark plugs/wires are about 6k miles old. I used Sea Foam through the intake not too long ago and cleaned the mass air flow sensor about 1k miles ago. I checked under the hood for anything obvious but didn't see anything. No vacuum leaks.

I have not done anything with the oxygen sensor, fuel filter, or fuel pump at any time (has 152k miles and I've owned it for about 15k, previous history unknown). Any ideas? It can't be THAT complex

 

[F14CRAZY]

I viewed some old posts and one mentioned the IAC. I'm going to check/clean that right now as I speak

 

[F14CRAZY]

I'm back in. I cleaned the idle air controller and swapped in the mass air flow sensor from my Limited (and I cleaned it). It's still hesitating a bit with no noticable gain. I did disconnect the battery for a few minutes before trying it and I did clean the terminals again, too.

Is it possible that there's an error code without the light coming on? I could get it checked tomorrow. My guesses now would be either the oxygen sensor(s) or something in fuel delivery (pump, regulator, filter, or sumthin). I can have my neighbor test that next.

 

[sawdust123]

You said you haven't changed the fuel filter. That was the first prob with mine. A good tune up wouldn't hurt either. Im going through kinda the same thing now as well so when I figure it out Ill let you know.

 

[F14CRAZY]

An elite with 66 posts!?

As far as a "tune up" what would be on your list? Doing the fuel filter does seem like a good thing to me and I'll do it tomorrow if I get a chance (haynes manual's here)

Thank you.

 

[MrShorty]

It is possible for there to be trouble codes in the computer without causing the CEL to come on. Pull codes and see.

Tune-up stuff, especially if it's due, wouldn't be a bad idea. Things to start with: fuel filter, air filter, spark plugs and maybe wires.

"From the exhaust it "putts" every second." -- This sounds to me like the sound mine made when cylinders 2 & 6 went out. You might do a cylinder balance test to see if you can isolate any misfire to a particular cylinder.

 

[merc2dogs]

check plugs, wires, coils and timing, if the timing's off I'd check the t-chain.
best indication of a timing chain is if you've noticed the power band move up a bit, as in having to get the r's up to smooth it out newer chains last longer, but they still don't last forever.

ken.

 

[Creager]

sounds like bad gas to me

 

[F14CRAZY]

I installed a new fuel filter today but it didn't help at all. I'm going to give up for today and mess with it more tomorrow.

 

[F14CRAZY]

I swapped in a known good coil pack from my Limited but it didn't help any. I've had a lot of problems with coil packs going bad and having the same symptoms but they were with older 3800s

 

[TPLYNCH]

Check your vacuum lines and caps. Make sure all wires to the plugs are connected tightly, and none are crossing/arcing.

 

[Creager]

this is a stretch...

bad motor mounts?

 

[F14CRAZY]

I checked it out today by pulling out the spark plugs. The middle plug on the driver's side of the engine (cylinder 5?) was crusted up. They're Bosch Platnium 4s I put in about 6k miles ago. It wouldn't clean up so I borrowed one from my Limited and now the XLs running good again. I'm going to see if I can pick up one replacement plug. The rest of the plugs on that bank of the motor were fine though. I didn't get around to checking the other side (which is a lot harder anyway) but I test drove it and it's back to normal.

Thanks guys. It wasn't an expensive fix after all.

 

[MrShorty]

Leaks through the lower intake gasket (coolant and/or oil) are known to be problems on the 1st gen OHV's in particular fubbering up cylinder #5. If you haven't tightened your lower intake bolts lately, I would jump right on that. I could be wrong, but it wouldn't surprise me to see you come back in a while with more problems with the #5 spark plug if you don't.

 

[F14CRAZY]

Thanks Mrshorty. I'll work on it again this afternoon.

 

[TPLYNCH]

I also recall people have not had much success with the Bosch plugs, although that might have been with the splitfires....

 

[F14CRAZY]

Sorry for the suspense. The spark plug of the middle cylinder of the driver's side bank gets bad every couple days now (150 miles or so). I can't yet tell if its getting covered with oil or fuel. All the other plugs are perfectly fine. I've been using Autolite platniums there. Obviously, something bad is going on.