My engine has all these problems intermittatly. The idle is rough, while cruising it misses, it backfires, and it stalls. Its a 305TPI. The engine itself is out of a '89, the ecm and wiring is the '85s.

While cruising around 65-70mph(2300-2500rpm) the car misses really bad or stalls but restarts or something. The rpms drop real real low then bounces right back.
At lower speeds(30-35mph) the engine misses, or starts choking, it has small backfires.
At a stoplight while in gear idle will be fine, then it starts to get real rough, like it wants to stall. Has stalled once.
While taking a turn at slow speed it acts rough and stalls occassionally.
All of the above is intermittant. The car will run perfectly fine other times.

I just replaced the fuel filter, wires, coil, cap, ignition module and air filter. The plugs were white, which means lean conditions correct? I didnt have the time to do plugs, i needed it running the next day. The rotor is the old one still, the cap I bought didnt come with a rotor, and i didnt realize it until i was home. Again, I needed it running the next morning and the store was already closed. Also has a new battery. The problems seemed to get real bad after the new battery was put in. My old one was kinda bad, but i think it got fried when a wire coming off the positive post fell onto the negative post and fried. The coil is a Accel Super Coil, the ignition module is a store brand, the wires are 8.8mm Delco's, the plugs are Bosch Platinums. The old rotor is Accel. The cap is Borg Warner.

I suspect my MAF is going bad. I pulled the plug from it, and started the engine, it seemed to idle the same as when its in. I have yet to try to drive around with it off.

O2 sensor was replaced just a little over a year ago. The ignition switch on the column was replaced last spring. IAC was replaced 2 years ago.

I checked for vaccum leaks but didnt find any. Checked fuel pressure, it was around 42lbs.
The EGR valve was replaced a couple years ago.

I dont know where to look. I think the air/fuel ratio is off and that is causing the majority of the problems, but I am not sure. Last spring I checked the injectors for any leaking, I pulled them and pressurized the rail while I looking at them, I didnt notice any leaks.

Also, before I knew the ignition module was wrong, my buddy wound up disconnecting the brown timing wire, then started the engine up. Is it possible that did something?

Any ideas?

 

what's your timing like? I'd put on a new timing chain and make sure that your chain isnt so stretched that it seems "off a tooth"

 

Was thinking timing, but I dont have a clue on how to check it or change it. Its sad, I can tear apart a transmission and put back togather no problem, but i can't do timing on a engine!

 

hehe, we're in the same boat I have a bit of book knowledge (because of this site, thanks to knowledgable people like Stekman, Ede, five7kid, Vader, and many others :hail: ) . I couldnt check the timing of my car on my own if my life depended on it right now. But once I have someone show me, I'll get it right away I'm sure.

If you're better at interpretting instructions than I am, then do a on "checking timing" you should come up with a ton of different things for it. Or you could take the easy-out and take it to a shop to do it, i think they'd charge half an hour of labor.

 

Was it ever plugged back in? If not, there's the problem. That tan wire is the EST wire. That is the wire used so the ESC system can tell the distributor what to do. Basically, it controlls the timing.

If it WAS plugged back in, proceed to plan B.

To check the timing, simply take out the inductive timing light, preferably with an advance feature. Attach one end to the #1 plug and the power leads to the battery, if thats how the gun is powered. Point it at the timing tab and pull the trigger. Off the top of my head, right now, I can't recall if yours is at 12 o'clock or 1:30ish on the timing cover. Basically, is what you are looking for is a metal tab that sticks out from the timing cover. It has a jagged edge with lines scribed into it. usually the big line is 0° or TDC. They go in incriments of 2 in either direction. From the front of the engine bay, looking at the tab, to the left is before TDC, to the right is after (As the engine rotates clockwise, as viewed from the front). There is a line scribed into the outer hub of your balancer. As you pull the trigger, the strobe light flashes when the corresponding cylinder is fired, in the case of you attaching to #1, it will flash when #1 fires. When it fires, the strobe flashes and you will see the etched line in the balancer line up with a line on the timing tab. You can tell the timing judging by where the balancer mark is when the flash lights it up using the description of the tab above. This of course, all hinges on the assumption that your balancers inertia ring hasn't slipped and your balancer still lines up with TDC. Then rev the engine to about 3000 RPM and check timing there, too.

To set the timing, you will have to find the EST wire and unplug that. it's a tan wire and should be located around the blower box area, against the firewall. This takes away the computers control to set the timing. Only do this is the timing is off. Once unplugged, loosen the distributor hold down clamp at the base of the dizzy. If i recall, it is a 9/16" bolt. There is a special tool for doing this that makes it easy. its offset to go around the dizzy and then back in under it. Loosen it just enough to rotate the dizzy by hand, but not loose enough that it can freely rotate. Rotate it accordingly to set the base static timing.

Is it throwing any codes? When's the last time the IAC and TPS have been serviced (cleaned the IAC and reset/adjusted the TPS)? To check the TPS, unplug the connector and hook up lead cables. Hook a DVOM up and check the idle. Should be .54ish. volts. If you have an old analog style, you can check for bad spots or whatever you wish to call them by hooking it up now and slowly opening the throttle. The needle should move evenly, with no jumping around. If it does jump, clean, replace, whatever you wish.

What all did you check when you looked for a vacuum leak? You can try a search under my name. I typed up a fairly thorough description of vacuum. Included were a list of things that were vacuum controlled. I think Sellmanb has the link.

If that doesn't work, proceed to plan C, which doesn't exist yet.

 

TPS i checked about a year ago, everything seemed ok. The IAC was replaced about 2 years ago. I'll have to check the codes, but the check engine light never seems to come on when its acting up.

The tan wire is plugged back in.

For the vaccuum leak I sprayed starting fluid everywhere on the engine. In the beginning of the summer I had the rails off, i was thinking maybe something worked its way lose.

This is really starting to be annoying though. About 2 weeks ago I had an ignition problem, thats what lead me to replace the coil, cap, wires, and ignition module. Also repaced the fuel filter then too. It drove around mostly fine until I replaced the battery, then it really started acting bad.

I was thinking maybe the cheapo ignition module is crapping out on me? Or another ignition component?

I'll check the timing as soon as I can. It sucks cause its my only car, and I need it to get to class and work.

Thanks for the help.

 

I was just thinking.

If it was a timing issue, wouldnt the problems be constantly happening?
Everything is intermittant, though now its happening more and more frequently.

More backfires too, though they are small, which leads me to believe a fuel problem?

Just a couple thoughts.

Thanks for your help.

 

Sounds to me like a fuel delivery issue of some sort.

Definitely not the timing. Put it back where it was, tighten it down, and leave it alone.

Most likely not the EGR either; just to get that other newbie type of knee-jerk "maybe it's the" out of the way.

Check your fuel pressure while it's doing it. Should be 37-38 idling normally, should go to 42-43 if you disconnect the vacuum line while it's sitting there idling; should lose no more than a pound or 2 after an hour of being left sitting after turning it off.

 

I havent messed with the timing, when it was in the shop a year or 2 ago they set the timing, as far as I know it hasnt been touched.

well I just checked the pressure.

With pump on and car off-42lbs
engine idling- 37-38lbs
idling with vacuum line off-44-46lbs
revving-jumps to 42-44lbs

it bogged slightly at idle, i didnt notice any drop in pressure though.

After the engine is shut off, the pressure holds, then drops slowly. Its still dropping as off now, I am going to wait a hour or so and check again. Right now its around 35lbs.

Thanks,

Matt

 

After about an hour, fuel pressure has fallen to near zero.

 

Likely you have a bad injector, or more than one....

Take them out and send them to www.cruzinperformance.com for cleaning, repair & flow-matching.

 

I just pulled the injectors out the holes and turned the car to run, got 42lbs pressure and not a single injector looked like it was leaking. I had my dad crank the engine to see if they fired. Every injector fired, and all the spray patterns looked more or less the same.

I spoke to Rich and cruzinperformance and he told me its not worth it to send my injectors into him. I have the Multec injectors.

Should I still test the injectors with a voltmeter, or should I take take that since they didnt leak and all fired mean that they are still good and not the problem here?

Thanks,

Matt

 

give your TPS a good cleaning again, it's been a year, things can happen Plus it isnt expensive, or hard to do this.

 

I was looking through some older posts and one said that if the fuel pressure drops after shut off sometimes its the FPR. The way to check is to pinch off the return hose and if the pressure stays, then its the regulator. I did that and it stopped the pressure from falling. So I got a kit for it and put in a new spring/diaphragm thing into. I then checked all the injectors again, I individually fired each one a few times, I found 3 that leaked, one actually didnt stop spraying, like it got stuck. 3 leaking/ sticking injectors could very well be a cause of the problems. But, pressure still bleeds off, faster at that. So, that would mean I have a leak somewhere still, or the FPR is still bad, or is there something else that could cause the pressure to fall off? Possibly the pump? Be aware thought that my pressure gauge is acting stupid, the bleed off valve is sticking and there is now gas in the needle face. I need to get another one that is known to be good.

I havent had a chance to put it back togather and run it. I need to get a voltmeter to recheck the TPS voltage and I am going to check and clean the IAC if necessary.

Thanks,

Matt

 

RB83L69 said that Fuel pressure on a TPI engine should only drop off 1-2 pounds, after the engine is shut off for a whole hour. Anybody else have an opinion on how fast fuel pressure should drop off after car tuned off?

My 305TPI loses all fuel pressure after several minutes

 

Listen to RB... he knows what he's talking about.

 

Check the TPS it can cause all that....Mine wasnt making good contact at the pig tail. The car would stick at 2000 rpms and idled rough, up and down it surged. All kinda weird crap. I gave it the jigle test while it was running and the idle droped down and would smooth out every time i moved the wire. I think i got some grease or dirt in the pigtail during the motor swap.

It just did little things at first then got worse. With the high revs.