Help! Serious Engine Problems (misfires) with midrange/top end

[saturnvii7]

Hey Guys,

I'm confused about a problem I'm having and am hoping someone can help. Car has been running rough the whole time I've had it, but recently it's developed some more serious problems that I can't determine the cause of easily.

A couple of weeks ago I put in some Lucas cleaner. Regular dosage, and it was running great at first. Then it started sputtering on start, and then the engine would run great once it warmed up. Went through a tank of gas after that but it did the same. Added some octane booster to the next tank. Now it's started having the inability to accelerate once the revs climb over 1500. I can't really take advantage of the turbo and for a brief period of time it was backfiring.

I've got a few throughts:1) Bad Cat could be causing problems with the backpressure- still have the original cat2) Bad gas or fuel management problems, although I'd think this would make my idle worse3) Bad ECU or ignition- is not sending the correct amount of fuel or bad spark plugs4) Bad Fuel Pumpand 5) (worst case) blown turbo

I'm thinking it's not #5 since it still builds boost. I'm thinking #1 because it sounds similar to other problems I've heard of people having and it had those nasty backfires briefly. Also the car has always run a little rich on the low end.

Please let me know what you think, or if you've had a similar problem

[evildky]

if the car was runnign fine why did you add the lucas stuff?

so does it not accelerate even after warming up now? if so I'd suspectt he fuel pump, it's real easy to go get an inline fuel pressure gauge, get your idle reading, witht he vac off the FPR it should be like 40 psi, with the vac on the pressure should drop to like 34 ish, when you rev the engine the pressure shouldn't drop below

if it's not he fuel pump it might be the afm, the FSM details how to test for dead spots ont he afm, it could also be a distributor or ignitor problem but I suspect the FP or AFM

another simple item check the connection at the CHTS, these sometimes get knocked off and cause excess rich condition fouling plugs

but if it idles fine and won't rev that kinda points to the fp, generally it starts limiting boost then the level gets lower and lower till you just can't rev, although I have seem them fail only when hot as well

[evildky]

I just noticed yours is an 81, so the distributor is hollow, so it's nto a problem, your cas is on the crank pulley

[saturnvii7]

Hey EvilDky

Well, as I said it's been running rough all along, so I occasionally used some fuel additive because it seemed to help it run a little smoother.

The power seems to come and go, so I suppose it could be the fuel pump. I might be best off just buying a new fuel pump, I've heard that NAPA has one for about $80 or $90 that puts out at 80 or so PSI. I'll check the fuel pressure first to see. It revs fine with the car out of gear and throttle application seems smooth then, which is what was making me think maybe the Cat. It almost feels like the exhaust is getting plugged.

I checked the CHTS yesterday and it looks to be fine. I don't have any resistors hooked up in line with it or anything either.

I'm thinking I should change the plugs regardless, and get an inline fuel pressure sensor hooked up. If I can determine that getting a new ECU (Standalone preferably) will fix the problem I'll go that route. If the fuel pump appears to be working fine, is there a way that I can test to see if the cat is clogged as well? Haven't made any changes to the CAS or AFM so I would think they shouldn't have gone bad this suddenly and seriously. Seems like the CAS would cause some more serious problems throughout all throttle levels as well.

[evildky]

CAS and MAS both can fail without warning, just because you havn't messed with them doesn't mean they work, sometimes when the cas fails, at least the ones form 82-83 that are internal to the distributor, they fail intermitantly and are more prone to fail at higher rpms and it's less noticible at idle than when loaded, of course you car is an 81 so it's an automatic, so you could in theory put the car in drive witht he parkign brake ona dn the wheels chocked and rev the motor for testing purposes (DO NOT RUN OVER YOURSELF IN THE PROCESS!)

your rough running might well be tied into this other problem if it's the AFM

[85300zxQuercioli]

I dont think you have a blown turbo, Dont most cars with a blown turbo shoot out alot of black smoke threw exhaust. I would check your plugs and wires how long since you changed them?

[saturnvii7]

Just replaced the plugs today. I'm trying to replace the 02 sensor as well, but it's rusted in there and I can't get it to budge. I might have to take it into a shop somewhere to get the O2 sensor swapped out. I had read somewhere that without the o2 sensor hooked up it should default to a failsafe tune where it should run smoothly, but having it disconnected doesn't seem to be having any positive effects.

I also hooked up an inline fuel pressure sensor, and it's at 32 PSI idle. I believe it's supposed to be at 38 psi so I'm guessing this could be an indicator that the fuel pump is on its way out. Is there anything else the low pressure could mean?

I also noticed that hitting the cat with a hammer results in a recognizable sand-like sound, which I've heard can mean the cat is clogged. Any suggestions from here? Should I buy a new fuel pump?

[saturnvii7]

actually, just noted that you said 34 with the FPR hooked up, so it's pretty much on target; 39 with that disconnected. so 33/39 should be okay... I haven't been able to scrounge up and friends to help so I don't have any way of looking at the fuel gauge with the throttle depressed...

I'll have to check through the manual and see if I can figure out how to troubleshoot the CAS and CHTS.

I'm planning on switching to the Z31 ECU soon. If the CAS is bad will I still need one for the new ECU, or would I have to switch to the distributor with the embedded CAS? I know it's a $300 part so I don't want to buy something I'm just going to end up throwing out later.