88 NA will idle. Won't Run. Code 51.

[CRE]

I've got an '88 NA. The car died on me on the highway. I'm getting a code 51. Don't have tools to test it, but I suspect it's the TPS. The car will idle. The idle is semi-erratic, but not very. Is the TPS the only thing that could cause this or is the AFM or possibly the ignition coil suspect?

 

[Nick M]

Many things can cause a bad idle.

51 means the idle contacts are not closed when you did the test, and the ECU thinks you are trying to acclerate slightly. So the air/fuel ratio is off. It can also come on if the A/C button is on, or you step on the acclerator pedal while testing.

 

[CRE]

For the most part, the idle is relatively stable, but I can't rev the engine above idle. Attempting to apply throttle results in sporadic firing...almost like a misfire but less consistent, and the car won't remain above idle at all with the exception of an occasional burst.

 

[CRE]

I think the code 51 may have been my fault, because I did try the excelerator while I'll had the diagnostic jumped, and if that would give me the code 51, than I'm not getting any codes. What is this most likely to be? AFM?

Could this possibly be a bad knock sensor? I haven't heard anything that sounds even remotely like a knock, and I'm not getting any codes. I'm assuming a bad knock sensor would throw a code.

Thanks.

P.S. - Right now the car is running, so I can't diagnose it, but I don't want to try driving it for fear that I'll get stranded in an even worse place.

 

[CRE]

Hey guys,

It's me this time... my wife's been posting for me while I was stranded roadside.

Well, after the car had some time to cool down it ran fine again. So, I'm thinking my fuel pump is on its way out and over heated. But, how do I test it if it's now running fine? Is the fuel pump most likely? Any other suggestions as for what to check?

Thanks!!!

 

[Nick M]

Make sure the harness is plugged in solid to the TPS. Besides the fuel pump causing a pressure loss, the fuel pressure up VSV could be bad.

Heat soak can also effect the ignitors on Toyota.

 

[CRE]

I don't think it'd be heat soak... I'm N/A and never had a problem until last night. Plus it's quite cool here right now and my temp under the hood is cooler than it's been in ages.

I'll look up the info on that VSV tonight when (if) I get home in my TSRM. Does that VSV control the vacuum to the FPR?

 

[CRE]

Update:

Well, the car drove fine all the way home. So I figured it was remedied with with one of the adjustments I made earlier today by the roadside.

Well, I tried to head out for a quick run to the store and didn't make it 20 feet.

On the up side, being away from traffic and with no wind I found that I am getting fuel.... actually, it smelled like the car was flooded. So I suspect it's not firing properly (although I am getting spark) and it's the ingition coil which is at fault. Anyone else concur? How can I test the coil?

Thanks!

 

[Nick M]

I don't think it'd be heat soak... I'm N/A

Not relevant. Even a Corolla can do that.

Plus it's quite cool here right now and my temp under the hood is cooler than it's been in ages.

If it was running bad when warm...

What color was the spark? A yellowish spark, or more of a bright white/blue?

 

[CRE]

I'll have to look again. I didn't pay attention to anything besides the fact that I was getting spark... at the time I was still clouded in the head and thinking it had to be a fuel issue. I really need to add a fuel pressure guage.

 

[JustAnotherVictim]

Everytime I've have a code 51 it was a tps problem.
Did you actually reset the tps or just play with it?

 

[CRE]

okay, so would a bad TPS cause what I'm experiencing? I didn't do anything with the TPS yet.

Just reset the ECU.

 

[Nick M]

Pulling the EFI fuse doesn't fix cars. Do that after you fix it.

 

[CRE]

ROFL.... I know. I cleared the codes because I hadn't checked the codes recently (and I've had to fix a nuimber of things since I last cleared them) and wanted to make sure that any codes I was throwing weren't related to something I've recently replaced.

So, I read the code 51, reset and checked again.

 

[CRE]

UPDATE: Well, I replaced my coil today, the old one was out of spec. BUT, that didn't fix it.

I've had time to verify a few things. I am not getting any codes. This is only happening when the car is warm. If it happens and I pull over and pop the hood for 30+ minutes it'll run fine until the temps rise again.

When this is happening the car will idle fine. The second you so much as tap the throttle it kicks and bucks and the RPM bounce all over the place. From the smell of the exhaust plenty of fuel is getting in... possibly too much.

My spark plugs, rotor and distributor have ~6000 miles on them. Replaced all my vacuum lines about 5 months ago. I've got 4 guage wire grounding everything under the hood (installed those lines about 4 mos. ago). I changed my oil about 2 mos. ago. I made sure my oil level is fine (check it very frequently).

I did just replace my radiator with a Koyo. Could it be dumping too much heat into my engine bay?

So, my thoughts are TPS, AFM, ignitor... Anythoughts?

 

[JustAnotherVictim]

Did you actually check the tps to spec or test the resistance?

 

[CRE]

When digging through my TSRM I must've flipped past the page with the specific resistances... I found it now, so I'll be checking those tomorrow.

I'm going to try to find a MKIII at a junk yard tomorrow... so hopefully I can grab a couple AFMs, TPSs, and ignitors to try out.

 

[CRE]

Spent the night fixing an oil leak and diagnosing my problem... My AFM is shot:


AFM Diagnosis Results

Test Result Spec. Tolerance


Temperature at time of test: 14ºC (57ºF)

Vs - E² 674Ω 20Ω - 600Ω
Vc - E² 280Ω 200Ω - 400Ω
THA - E² 3.15KΩ 3KΩ - 4KΩ
Fc - E¹ Inf. Inf.


Temperature at time of test: 62ºC (140ºF)

Vs - E² Inf. 20Ω - 600Ω
Vc - E² 281Ω 200Ω - 400Ω
THA - E² 920Ω 400Ω - 700Ω
Fc - E¹ Inf. Inf.

Conductivity between Vs and E² was regained after the temperature dropped to 17ºC (63ºF) giving

1.9KΩ.


Temperature at time of test: 26ºC (78ºF)

Vs - E² 1KΩ 20Ω - 600Ω


Temperature at time of test: 37ºC (99ºF)

Vs - E² 1.8KΩ 20Ω - 600Ω


Temperature at time of test: 41ºC (106ºF)

Vs - E² Inf. 20Ω - 600Ω




My TPS tests properly, but the resistance doen't move smoothly when the throttle is moved, it spikes.... like you'd expect from a 20 year old wirewound pot.

I just figured I'd close up this thread with the final results.

 

[JustAnotherVictim]

TPS skiping is normal from my experience even with new parts.

 

[CRE]

TPS skiping is normal from my experience even with new parts.

Yeah, I'd expect some... I'm not really worried about it right now though since I've found that the AFM is what's dying....

Perhaps I should just water cool my AFM? I could probably get another month out of it.:evil2: