[Racefiend]

OK, I have a hesitation problem that I can't figure out. The engine misses irradically. I checked each coil, and if I put the light on the left wire of any coil, the light flashes normally, but every few seconds the light gets constant for a split second, then back to regular flashing. The right side wire of any coil pack flashes normally, with no noticable irregularity. Timing is constant but every few seconds it wavers ~ 5 degrees. Pulling each injector wire produces a difference on all cylinders.

So far I've done:
Injectors were cleaned/balanced
Changed fuel filter
o2 sensor changed
Changed coil packs with known good packs
Changed ignitor with known good ignitor
Changed plugs
Changed wires
Changed ECU with known good ecu (and checked ignitor voltage at ecu...good)
All vacuum/intake hoses good
Compression check was even 140psi (+/- 2psi across all cylinders). HG changed ~2k miles ago, with head rebuild and valve cleaqrance set.

Tomorrow I'm gonna try to swap the CPS with a known good one, even though the pickup coil resistances check out ok.

Any thing else I can check? I'm starting to get really pissed.

Thanks guys

Christian

 

[Racefiend]

Oh, one more thing, when I unplug the Idle Control Valve, the idle doesn't change at all....should it? Idle was set using adjusting screw on TB

Christian

 

[sabolt1]

Sparkplugs?

Coil Pack ground?

 

[Guest]

Any computer codes?

How exactly is it missing? Under load, decelerating, WOT, etc etc.

If you unplug the ISC, it just stays in the position it was when unplugged. Hence no change in RPM.

The adjusting screw on the TB isn't an idle screw. It is for your dashpot system. Doesn't your car idle on its own?

Have you checked your timing belt yet? If it is loose or worn out, it can produce some strange timing issues, since the CPS is driven off of it.

 

[Nick S.]

i was having exact same prob man!

dropped my car off at Urbanos and got a brand spankin' new engine wire harness and since then ALL probs have been solved!

 

[Racefiend]

Sparkplugs?

Coil Pack ground?

Replaced plugs, ground good.

Any computer codes?

How exactly is it missing? Under load, decelerating, WOT, etc etc.

If you unplug the ISC, it just stays in the position it was when unplugged. Hence no change in RPM.

The adjusting screw on the TB isn't an idle screw. It is for your dashpot system. Doesn't your car idle on its own?

Have you checked your timing belt yet? If it is loose or worn out, it can produce some strange timing issues, since the CPS is driven off of it.

I checked the codes last night, and got a code 14, but I checked voltage at ECU and had juice between both IGf and IGt, and E1. Thats when I replaced the ignitor. Reset ecu and haven't got the code again.
I can really only notice the miss at idle. However, the car has some nasty vibrations which have gotten worse, and I'm assuming it may be the miss.
As far as the idle screw, we talking about the same screw? Not the one on the linkage, but the one inside the little tunnel on top of the TB. The car idles on its own, but not where I wanted it to, so I fine tuned it with the idle screw. I'll recheck the belt, too. I replaced it when I did the HG, but who knows....

i was having exact same prob man!

dropped my car off at Urbanos and got a brand spankin' new engine wire harness and since then ALL probs have been solved!

I wish that was an option. A new harness is mucho $$$. But I swapped the harness over from my 87, which ran tits, so I wouldn't think it would be bad. Maybe I'll try adding some grounds to see if that helps it too.

 

[drjonez]

'89+ TBs don't have the idle air bypass screw....kinda sux!

as for your miss, i'm pointing to the CPS or the wiring harness. remember the harness is old and crusty and ANY movement can result in breakage....

FYI- you can't buy <'88 turbo engine wiring harnesses new any more....

 

[ma71supraturbo]

FYI- you can't buy <'88 turbo engine wiring harnesses new any more....

Elmhurst Toyota has a few. I was quoted >$400 for an 87t automatic harness. When I caught my breath, I opted for the Radio-shack method

 

[Racefiend]

GROUNDS GROUNDS GROUNDS

That was my problem. Whenever I tested ground from the engine (plenum) to the batt post, I got .4 ohms. Nothing wrong there, so I figured grounds were good. Today, after finally replacing the CPS with no results, I decided to check the ground again. .4 ohms again, then I started the car and tested again (never tested it with the engine running). This time the resistance jumped up to 14 ohms! Bam! I got a big smile on my face. I added some ground wires and the engine runs tits! No more miss and the spark is totally regular. And now, with engine running, I get a resistanfce of around .1 ohms. Whew, this has been pissing me off for quite some time. Now on to figuring out my vibration problem.

Christian

 

[Supranforever]

What grounds would I check, I've checked everything but the grounds on mine, and it seems to miss just a tad bit at idle and when I suddenly accelerate. I think I may need to clean my injectors also though, could this cause it?

 

[Racefiend]

There really are only 2 ground points for the motor itself. One from the neg batt post to the block, and one from the head to the firewall (near turbo). Check the wires and make sure they're good, not crusty, and have no resistance. There are a few sensor grounds on the motor, though, most notably being the one under the intake plenum (where it meets the runners). There are two ring terminals bolted to the plenum that have 5 wires. These are the various sensor grounds. Make sure the terminals are clean and make good contact w/ the runners.

To check how well your engine is grounded (important, since your sensors use the engine as a ground point) get your multimeter and test resistance from your intake plenum to the neg batt terminal, both with the engine stopped and with it running (as I found out today, it makes a difference). Anything more than a couple ohms and it might be a good idea to add some grounds.

What I did is add a 4 guage ground wire (available at autozone) from the negative batt terminal to the intake runners, on the same bolt that all the sensor grounds bolt to. Then I daisy chained some 10 guage wires across a few points on the intake/head and then to pass side chassy. I didn't add any to the block, as 99% of the sensors are grounded on the head/intake/etc, and the head is somewhat isolated from the block by the HG.

HTH

Christian