After being parked for 2 years my 94 Loyale has a 'jerky' and sluggish acceleration.  Worse at lower rpm's and some days are worse than others.  Also, a few days ago the engine quit without warning twice while driving uphill.  Started back up a minute later.  Not sure if this is a related problem. Either way, I'm suspicious of the fuel system and specifically the fuel pump, but I don't want to start throwing parts at it if it can be avoided.  I've considered a plugged Cat, but the exhaust smells normal and seems to have good flow out the tailpipe.  No relevant codes from the ECU present.

 

I've run a tank of fresh fuel with a can of Seafoam through it and done a full tune-up including all filters and ignition components.

 

Has anyone had a similar experience?  Any suggestions on where to begin troubleshooting?

 

Update:  Its not the fuel pump

Edited August 27, 201510 yr by jetpilotdc10

i have the same issue on my 1990 loyale but not nearly as bad once it warms up only when its cold otherwise it runs really good

Jerky acceleration at lower rpms typically is just a throttle body issue. Basically it just needs a cleaning and the probably should be significantly better. I recently bought a 96 impreza that wasn't driven much for a while. Similar jerky acceleration, did a fuel injection service (it cleans the injectors as well as the throttle body) and it was good to go afterwards. Though, I did physically take the intake hose off (the one that connects to the throttle body) and got in there with cleaner and scrubbed it clean with basically a toothbrush (my throttle body was really dirty)

But, with the engine dying while driving uphill, I don't think that would be a throttle body issue. That could be fuel pressure etc etc...

Did you remove the TB or just spray/brush while on the engine?

UPDATE: Tested the TPS.  It seems good, but slightly out of adjustment.  I feel like this would affect the idle more than anything.  Cleaned the TB and went for a short test drive....no improvement.

Edited August 28, 201510 yr by jetpilotdc10

When you say you've done a tune up and all filters. Did that include the fuel filter? If not, remove the filter and blow through the in side. It should be fairly easy. It it is restricted at all, that could cause an issue with it runner.

The only things in the fuel system I haven't inspected, repaired, or replaced, are the fuel injector and pressure regulator.

When I first got my 93 loyale the check engine light was on and it was the egr valve solenoid and my csr kinda felt like that with the sluggish and jumpy acceleration.

Does anyone think it could be a bad injector?  When I bought the car the timing was all messed up.....while attempting to start it, the engine backfired out the intake several times.  Almost blew a hole through the air filter.

 

EGR and purge solenoids have been replaced.

I also have a similar issue in my '88 DL (AE81?). Seems that it has less of an issue now that I run 91 octane, but it still seems iffy. In fact, starting the car can be a weird process as well. I am yet to find the problem out. 

Edited September 8, 201510 yr by Casull

Casull, what have you tried fixing/testing/repairing?  After maintaining/repairing all my own vehicles for the last 20 years, I've never been so stumped on a problem.  I'm just about to admit defeat and take her to a shop.

You should check your grounds. Especially the one at the manifold on the passenger side and the connection at the battery. It is possible for the injector to be plugged up, but you said you have cleaned the throttle body? You can check the spray pattern with the boot off and MAF disconnected. Youll have to clear codes after this. A dirty/failing mass airflow sensor (MAF) is another possibility if your symptoms dissapear with it unhooked it would be a possibility.

Whats the status of your ignition system?

Ignition system has pretty much been entirely replaced.  Coil, dizzy, cap, rotor, wires, plugs.

 

I just discovered there's a drop in exhaust temperature after the 2nd cat. Temp rises after the 1st one. Not sure if this is normal on these cars or not, but I'm going to investigate this further.

Edited September 2, 201510 yr by jetpilotdc10

Well the exhaust seems to be functioning normal.  The last thing I can think to do is inspect/swap out the fuel injector.  The MAF sensor is sparkling clean and tested ok.

Dont blow off thise grounds either. Check injector spray pattern, if its gummed up it will "pee" instead of spray.

Well the fuel injector is certainly spraying fuel, but that's about all I can tell. Not sure if its doing it correctly. Looked like tiny bubbles dancing around on the throttle plate.

Edited September 4, 201510 yr by jetpilotdc10

Needs to be a nice mist use a bright flash lite, timing light what ever. You did check fuel pressure, right?

Major breakthrough!

I drove with the MAF sensor unplugged and it runs perfect!  The MAF sensor passed all tests and I don't have a code for it, but it must be the culprit here.

If you have one handy Ide totally try it. The catch to this test is that running without it forces the ECM to run the engine using the CAS, temp sender, and tps. So there is a small chance having it disconnected is simply hiding the problem. If it were mine ide swap it. Fingers crossed for you.

Swapped it off my other (perfectly running) Loyale......same problem

 

Im pretty sure that disconnecting the MAF sensor would make it run richer.  I've always felt that this has been a fuel starvation issue.  So my next question would be what is causing it to run lean when the MAF is connected?

Edited September 4, 201510 yr by jetpilotdc10

It would definately make the car run richer, over all. Did you check the grounds I mentioned yet? - this is important, if you ave an increase in resistance in the ecm ground it could throw off all the sensor readings.

Inspect your intake boot, thoroughly, for any cracks. Check where the elbows meet the boot and the elbows themselves (make sure the fit tight).

Next... Try removing the vac lines from the EGR and the evap canister, plug them and take a drive.

Fuel pressure under load?

All the grounds I've found are on the drivers side, except for a couple wires I repaired connected to the t-stat housing.  Intake boot is checked and good.

I can removed and plug the egr hose.....which one do I disconnect from the evap canister?

Do you think this could be related in any way to my code 55?

Can't help but wonder if there's a vac leak, mainly thru the PCV system.

 

Reason for that thought is it seems to be running "Lean" for the most part, but disconnecting MAF makes it  "rich" and it runs better.

Really sounds like vac leak.

 

Don't know, just thought at large. And PCV system hasn't been mentioned yet

Can't help but wonder if there's a vac leak, mainly thru the PCV system.

 

Reason for that thought is it seems to be running "Lean" for the most part, but disconnecting MAF makes it "rich" and it runs better.

Really sounds like vac leak.

 

Don't know, just thought at large. And PCV system hasn't been mentioned yet

Agreed, and leak small enough that it isnt effecting the idle may become large enough to throw off the MAF readings under load. Perhapse a set of vice grips to close off the hose connected to the pcv could serve as a test for the valve itself.

 

Might as well plug both lines to the evap canister. Also eliminate the solenoids as a leak point by making your plug at the lines feeding them. - long shot...

Edited September 4, 201510 yr by ihscout54