sqzbox

My computer is being a b***h and giving me the silent treatment! WHY? My problem? I turn key on, pump runs shuts off and I start it then it dies. This might happen 3-4-5-6 times before it stays running. It's starting to happen more frequently now and performance is down. I drove it to get some gas today ( about 5-6mi) after warm up and it was slugish, hesitating, and lacked power. If I mash on it , it picks up, but not like it should or was. I also noticed than when I back off the gas it seems to want to take off!! Something ain't happening like it should. Let me guess, fuel pressure? injectors? no spark adv? bad coil? Why no codes? shouldn't the comp. pick up on this? I've changed the Oil/fuel pressure switch, fuel pump relay, gas filter, plugs to rotor, Cleaned the IAC valve and the egr. Everything is stock Lo3 1988 execpt for 3" cat back. I wish it would roll-over and DIE so it will become obvious! WTF is going on. I've been putting up with this off and on for about 3 yrs. ( I don't drive it alot about 3000 a year) But it has recently started getting worse. Has this happened to anybody else out there? Or am I the only lucky sob with this problem?

Nixon1

You'd be SURPRISED at how little the computer will actually notify you of sometimes. On my Ford, I can entirely DISCONNECT the EGR valve and not receive a check engine light. How's that for technology. It's not that the computer doesn't NOTICE...it does....it just doesn't want to tell you because it figures, 'well if I told him of every little thing running wrong, he'd have a check engine light 24/7!'

Even though you've cleaned the IAC valve, don't entirely dismiss it...the motor may be weak and not wanting to operate properly.

This actually sounds a lot like an MAF problem to me though.

sqzbox

MAF on a throttle body?

Nixon1

Sorry..my fault, didnt read that. Well hell...I don't know much about TBI motors.....

sqzbox

Sokay! I thought I did!!

Vader

Idle vacuum = ??"

Idle vacuum with EGR vacuum line disconnected and plugged - ??"

Vacuum with brake booster and PCV unplugged and capped?

What is your base timing setting? Do you measure an increase in advance when you reconnect the EST bypass?

sqzbox

Vacuum is 23in. at idle. Dismounted Egr and cleaned it and checked it for movement and reinstaled it. Same thing with the IAC valve. Never thought to check adv. rate, good idea! Base timing is at 4*. I didn't dismantle the IAC, I just sprayed some chock cleaner up it's A** and the black just poored out of it. I cleaned the tip with a rag and gave it a drop of 3in1. The way the motor picked up power as I backed off the peddle from full throttle makes me think it could be lack of fuel pressure or lack of timing adv. Lean to rich or less demand of adv. timing. I'll check the timing Friday my next day off. I need to get a fuel pressure gauge but napa wants 58 bucks! is that resonable? or is there someone who has them cheaper. Thanks for the reply!

Nixon1

4 degrees is weak timing. Dont these motors run 6 degrees stock?

sqzbox

The book and the under hood sticker call for 0* on an 88 Lo3 formula.

Nixon1

Really?? Man, that's odd...

rodrigo diaz

HAVE YOU CHECK FOR CODES MY FRIENDS 88 WAS BARELY RUNING ONCE BUT IT WOULDN`T GIVE ANY CODES NOT EVEN CODE 12 SO I CHECK THE MANUAL IT TOLD ME THAT IF THE SES LIGHT WAS GOOD THEN THE COMPUTER WAS DEFECTIVE , WE BOUGHT A REBUILT ONE AND PROBLEM SOLVED

sqzbox

Odd? not really, 88's are by themselves so I hear. Even the prom chips are different than other years. Thats why only special people (like me) are allowed to own them!! LoL!!!!

Vader

O.K. So, do "special" people load their accordian into their ThirdGen from the side door or hatch?

{BTW - It's Friday. Any news?)

sqzbox

Hatch! No news. The butt heads reniged on my vacation day. Had to cancel the golf with my two boys Seems they just had to have a load of pumpkins delivered.:lala: Our towns fall festival starts today and I'm obligated to that now, so maybe tommorrow I can do my stuff!

sqzbox

Drove the car to sears today and got the new tires rebalanced. The car ran like crap ( a little sputering and hesitation) for about 10 or 15 mi. then smoothed out. still not the perf. it had. Started it 5 more times during the day and it screwed up every time. Here's what I did to it today. Took the IAC valve back out, disasembled it, cleand it and reinstalled it and followed the books directions for adj. after adj. I observed the operation and it seems to be working. Open at start up and slowly closes for smooth idle Took vac. readings with all of the above (egr disconnect and pcv, and brake booster) vac was normal 22-23 in. steady. Checked timing rate of adv. and wierd starting showing itself! With the spark control link connected I crack the throttle open and the timing jumps backwards (towards 0* engine hesitates) and finally starts to adv. I rev it up to 3000 and it only adv. to about 20* thats as far as it will go. Shouldn't it go about 30* ? counting the 4* init. for about 34 total? And shouldn't the timing adv. right off the bat? I also pinched off the fuel return line and it made no diff. at any rpm. that's all I've got for today! After I cleaned the IAC valve I haven't got it to screw up again (about 4-5 times) but I haven't driven it yet ? I'll get back after that>

Nixon1

That timing shouldn't be retarding before it's advancing...

You say you observed the IAC valve working...how could you tell? You saying "slowly closes for smooth idle" makes me wonder.. I'm pretty sure the IAC valve is a 2 position valve, open and closed, and it's supposed to act very quickly...if it works too slowly it'll cause stalls and bad stumbles during braking, deceleration, etc.

sqzbox

With the engine off and air cleaner removed you can look down a hole in the TB and see the end of the pintle backed out. When I start it and runn around the car and look I can see it closing, when it does the idle smoothes out ( takes about 8-10 sec. for it to close.)

Nixon1

I keep forgetting you have TBI. Nonetheless, that sounds like it's closing way too slowly to me. If I had to guess, I'd say the motor is shot. But again, I could be wrong.

sqzbox

Man, I hope your talking about the IAC motor!

Nixon1

Lol, yeah I am. I wish my Haynes manual tells whether the IAC valve is a variable speed motor.. Because during rapid decellerations and stuff, it'd need to operate quickly..but at idle it wouldnt. If it IS a variable speed, then yours is probably just fine...

sqzbox

I think it's sopposed to be variable. It's supposed to let a little more or less air in on 88 Lo3 Otherwise it would be solinoid opperated for instant open or closed position right?

Vader

The IAC on our cars is a stepper motor (like the EGR valves on later vehicles). The ECM will pulse the stepper coils (two of them) in the proper phase (sequence) to move the rack gear either inward or outward. The rate of the pulses is what controls the speed of the pintle. A typical ECM only performs an output table update 11,000 times a second. Unfortunately, the propagation delay of the real world outputs is much slower, so the ECM is instructed to only update outputs at a maximum of about 300 times/second. Even at that rate, the IAC should be able to step from full open to full closed positions in about two seconds. If your's is slower than that but is still working at all, it is probably dirty. It may have a worn set of gears, but is more likely dirty. Remove, disassemble, clean, and lightly lubricate it.

sqzbox

Hey man, did that today! cleaned it real good, followed inst. on reset too. It closes real slow and I have to nurse it till it closes before it idles worth a damn. Guess I'll get a new one! Any idea on the timing thing? (above post)

Vader

Don't get too excited about replacing the IAC just yet. You still have a timing problem, and no one can guess the internal stuggles the ECM is battling.

Have you disconnected the ECM power to clear all codes, stored VRAM, and junk it may have in memory? Is the SES working at all? Is the EST working?

sqzbox

Yeah, cleared codes and all. SES light is working. recently got a code 32 in the last month and fixed that. How do you check the EST? I put a T light on it yesterday with control wire connected and when I crack the throttle open The timing drops back towards TDC, hesitates, then starts to adv. only to about 20* at 2500-3000 rpm. I don't have a timing light with an adv. dial but it's only showing adv. the same distance from 10* as there is from 0* to 10* on the timing tab on timing cover. Last night it started screwing up again.
turn key on, pump runs, engine fires, fast idle comes up then surges up and down till it dies, then pump continues to run about 3 sec. and stops. I did this about 10 times with the same results. I finally fired it up and dove under the hood and masterbated the throttle till I nursed it up to 2000-2500 and held it there untill it smoothed out and IAC valve finally closed and then it idled ok but performance is down. If you drive it about 15 mi. some perf. returns but untill then, it hesitates intermitenly every time you accelerate from idle or part throttle.

Nixon1

LMAO...

That engine sounds pretty out of it man. I still dont understand why it retards the timing before it advances it. It shouldn't be dipping at all... Since the EST is disabled when you check it, I have to assume that there's something wrong with your distributor's mechanical advance (if my terminology is right)...

sqzbox

My spark control wire was connected. I was checking to see if I had ANY adv. working at all. Don't think the EST system has any mech. adv. It's all controled by the ECM.

Nixon1

What I meant was, if you have the EST off and rev the engine, the timing will advance itself even without the ECM involved I believe. Try this...it's not healthy but see if it makes your car run better. Disconnect the EST and run slightly higher timing than normal as your base. Then drive the car without the EST working. It's not GREAT to do this all the time, but it won't hurt anything for a short period...test the car and see how it does. If it's smoother and gains power, then there's something wrong with your EST system.
The EST, from what I've witnessed, usually adds about 10-15 degrees of timing at idle.

My old V6, which ran 10 degrees of base timing WITHOUT the EST...it ran between 20 and 25 at idle with the EST and when you revved it, the timing shot out past the mark (over 30 degrees advance).

sqzbox

I'll try that next chance I get! I've got to get ready to hit the road again. I'm home through the week so maybe I'll get a chance before next week-end Thanx!

Nixon1

Any time man. Let us know how it goes.