Tampa 928s

Attached are the Lm-1 data logs that show the drop out while under cruise. This manifests itself as a skip under normal load while cruising. The timing of this skip is for a 1/4 of a second and is intermittent. While under full boost all the readings look fine, this must be electrical and need a place to start looking.

Checked:
Pin Connectors for Ezk and Lh on harness
All grounds
All electrical connections
Relay is not a 53 but a large style 1.5 times longer in length, original

As you can see the all values drop like the key was turned off.
Maf
Rpm
Inj
O2 Spikes just before it shuts down

This was not happening before the S/C install so its something I must has disturbed.

Posted in Toothed belt thread by mistake!

Tampa 928s

No, but logic says everything was fine before the S/C install, trying to see what else could cause this and how to ID it.

AO

WWJBS? Relay relay relay!

Three things come to mind, relay, ignition switch, or a ground fault in the fuel injector circuit.

You might try logging the voltage to the LH to see if that ever get interupted. If it does, then it's more than likely either a bad relay or a bad ignition switch. A relay is way easier to swap.

John Speake

Try disconnecting the rpm input to the LM-1. Didn't you say you had some problems with that feed ?

Worth considering that it's the LM-1 causing the problem. Easy to eliminate....

Tampa 928s

Try disconnecting the rpm input to the LM-1.

I will try that first!

My question is the Lh relay is a much larger unit then the normal 53's is this because of a current draw requirement, should I look for a exact replacement or will the 53 work OK?

AO

I doubt the LM-1 is causing it. It's basically a digital volt meter. Sorry, I don't know about the relay on the 85/86 cars.

John Speake

type 53 should be OK, the LH relay is not the most highly loaded. The fuel pump relay has the highest current of the 3 that enable the engine to run.

Although it is unlikely that the LM 1 is causing a problem, it would make sense to retrace your steps, and disconnecting that is an easy first step.

Does the step occurr at the same rpm each time, or is it completely random ?

Tampa 928s

It seems to be random as far as Rpm's go, notice it when cruising 2500-3000.
I like the idea of using The Lm-3 to monitor the voltage since it's input is rated at 5v, would would this be possible.
I think that the LH is the place to start, EZK and finally Fuel Pump Relay.
Any other area's to poke around to monitor other then removing each Lm-1 connection one at a time to eliminate each potential problem area ?

Z

In the log named surge 3, you can see several places where the fuel injector duty cycle spiked higher and the air/fuel ratio spiked rich right afterwards. Something caused the injector duty cycle to increase briefly, and the mixture got richer in response to the injectors delivering the extra fuel. When this occured, the RPM, and manifold pressure remained stable, so the jumps in the injecor duty cycle were not a result of increased throttle opening. The MAF signal also remained stable so the jumps in the injector duty cycle weren't the result of any kind of MAF problem causing a higher load cell of the fuel map to get used by the LH computer. Besides the possibility of a problem with the LH computer, there are a few things that could cause the it to increase the injector duty cycle.

A bad temp-2 sensor, or a loose or damaged wiring connection between the temp-2 sensor and the LH computer could be causing it to recieve an indication that the engine is colder than it really is. The computer will think that the engine is cold and will then increase the injector duty cycle in reponse, to add fuel for cold enrichment.

The full throttle switch or the wiring between it and the LH computer could have a problem. If that switch is closing when it shouldn't be, or the wire for it is shorting to ground somewhere, the computer will increase the injector duty cycle to add fuel for full throttle enrichment because it thinks you're at full throttle.

The O2 sensor or the wiring between it and the LH computer could have a problem. If the O2 sensor signal that the LH computer receives is low, it will think that the mixture is too lean, and it will increase the injector duty cycle to make the mixture richer. It might be worth unplugging the O2 sensor from the computer to see if the problem then goes away. If it is a wiring problem between the O2 sensor plug and the LH computer, the problem may still occur with the O2 sensor unplugged though.

The log file named surge 5 looks like it might be a different problem. The way that the signals spike down would make a temporary power loss seem like a possibility, but the boost and and injector channels don't spike down like the other channels do. If there were a power interruption, the boost and injector channels should have dropped like the others did. The acceleration channel drops, but it occurs a little bit before the other channels drop. That also makes me think that it's not a power disruption problem, or they'd all be occurring at the same time. The air/fuel ratio was one of the channels that dropped. Since the air/fuel ratio is taken care of by the LM-1 and the other channels are fed into the LMA-3, it wouldn't seem like it's a problem with the LMA-3. If it was, I wouldn't expect the air/fuel channel to be affected, unless maybe it was corrupting the data stream to the point that it affected the air/fuel data added later on by the LM-1.

Are you sure that the cables are fully seated in the LM-1? I don't know if it's still an issue with the newer LM-1 units and cables, but with the earlier ones the mini-DIN plugs didn't really go in as far as they should have on at least some of them. The holes in those LM-1 cases were round, and the two corners of the mini-DIN plugs kept them from going all the way in. The corners of the plugs could probably be trimmed to allow them to go all the way in, but I cut the case of my LM-1 instead. That way I don't have to worry about it when plugging in different cables or moving the unit into other cars. I cut the holes for the mini-DIN plug locations in both the bottom and side of my LM-1's case.

Tampa 928s

Z

I changed out a relay for the Lh and checked all the connections near the panel.
I will follow up with your suggestions. Today is started to do it several times and more severe, I logged it. The Rpm's on the dash stayed steady, two times the Rpm's went to 0 and bounced back and car stalled after heavy acceleration.

Tampa 928s

Car will not start without feathering gas this morning when cold.

Tampa 928s

Still cold, idle jumps from 1.2k to 0 trying to stabilize smells rich. The Temp switches ohm out ok.
After I feather it for a while it will idle, so this is a cold start issue it ran fine a few days ago. I can assuming this is all related to my drop outs.

Tampa 928s

Started car running super rich blowing black smoke!

Kevin Michael

Welcome to my world Tampa! I had that low rpm drop-out to lean at 2500-3500 rpm for a split second ever since my install 2 yrs ago. Everything and anything has been replaced even the computers. Some things even twice to rule out a bad part. My black smoke seems to be getting better and is not there all the time. But the black smoke and fluctuating idle till warm are definately related.
Kevin

Tampa 928s

I put the AA chips back in and double checked the Ox sensor. I did find the replacement connector broken and this may have been shorting out the Ox sensor. I went on this path after seeing the A/F gauge stay rich all the time. I repaired temporally the ox sensor connector and still has the Rich condition.