Diagnostic tool for -94 TBI engine?

[DavidF]

RE: Diagnostic tool for -94 TBI engine?

I talked to Mark over at PCM to get the proper spec on fuel pressure and TPS setting. He said 13.5-14 psi for the fuel pressure. I cannot get below 15psi. TPS should be .5 volts. He said my .53 volt setting is fine.

But, most importantly, he said parts are still available for the TB EFI systems including the ECU. I have also heard that PCM has parts for the Pro-Tec ignition systems that they are only selling to customers that have EFI engines as the EFI relies heavily on the Pro-Tec ignition...this includes the coil packs.

[cpconsulting]

TPS check and adjustment

How do you check the voltage and make voltage adjustments on TPS? Is it just a matter of rotating the sensor?

Also, how do you determine if the IAC is functioning properly or not? My idle is at around 910rpm. I don't have any vacuum leak anywhere.

[DavidF]

RE: TPS check and adjustment

My idle is high as well, plus the engine is running rich after the TPS and IAC have been replaced. I adjusted the IAC yesterday and have not tested at this time. But...

Adjusting the TPS: Using a voltmeter, probe pins "A" (-) and "B" (+) to measure voltage from the TPS. At idle, the voltage, according to Mark at PCM, should be .5 volts and 4.5-5.0 volts at WOT. Adjust by loosening the screws holding the TPS to the TBI unit and rotating the TPS slightly, as you read the voltage. I simply push the meter probes into the back of the connector where the wires enter the connector. The voltage of the TPS should smoothly (linear) change between idle and WOT without any spikes or flat spots.

The IAC: The IAC can be adjusted for maximum throw only. However, a previously installed and working IAC either works or does not and should never need adjusting. With a new IAC, you must ensure that the maximum throw will fully close the bleed air passage. If it does not, remove the IAC, push the spring loaded black sleeve back into the body of the IAC, then rotate the pintle counterclockwise to increase the maximum throw. Before releasing the spring, make sure the end of the spring engages the slot in the back of the pintle to ensure the pintle adjustment cannot change. The computer then takes care of the rest by retracting the pintle sufficiently to maintain idle speed at the predetermined value of about 700 rpms. Remember that the IAC is buffered...meaning that it takes some time to bring the idle back to normal after the throttle is closed. This is supposedly designed to keep the engine from stalling when the throttle is abrubtly closed. However, I believe it is more of a function of the response speed of the IAC. You can verify if the pintle is operating by looking into the air bleed hole or by placing your finger over the air bleed hole...the idle should drop, then after letting go rise above normal briefly before settling back to normal.

So, now that I have been sufficiently wordy, how does your engine run otherwise? Mine seems to have an inconsistant rich idle. Also, the engine stumbles badly at steady throttle between about 1500 and 2800 rpms, but smooths out at hight revs. I have not tested since I discovered the required adjustment of the IAC as described above (yesterday) and I am hoping that I have both problems now cured. Seems to run better on the fake-a-lake.

BTW: Mark at PCM recommended the fuel pressure to be between 13.5-14 psi even though my PCM manual states 15 psi. I also adjusted that yesterday.

[cpconsulting]

The boat runs and handles great. Never had any problem with it. It runs strong from idle to slalom speed and beyond. No hestiations whatsoever in the entire powerband. All the fluids stay clean, as I change the oil every 50 hours and tranny oil very 100.

[mf01]

Sorry to beat an old thread, but I have a starting problem with my 94 TBI. It takes about 3 good key cranks to get my engine started. Once it is warm, it starts right away. I have replaced fuel filter, changed spark plugs, and oil/filter. I let the fuel pump prime before I try to start it. I even have turned it on then off then on a few times, to make sure that the fuel is getting primed all the the way up. It still seems to be 3 good key cranks after the boat has been sitting for 6-7 days. I'm beginning to think that it is one of the sensors.It might be the CTS (coolant temperature sensor) as it seems to vary the fuel inputs upon startup. Another thing, the boat runs great after it has been started. Does anyone have any insight? Thanks.

[dba4life]

Hi mf01 - I have the exact same condition with my 94 Sport with the 5.8 proboss tbi and pro-tec ignition. I cannot seem to solve the problem. It is very inconsistent. Will start occasionally. Most times I have to give just the slightest squirt of starting fluid to get it going. Once it starts once - Starts everytime no problem.

I have done everything you mention above. Including the CTS.

[wmbuono]

Sorry to open up a very old thread but I am having the same issues as DavidF. I haven't yet looked into the MAP sensor but that is first on my list. I am mostly curious about the intake air sensor. I found it in the manual from SkiDIM but have had little luck finding any other mention of it. Does anyone have any insight into these sensors?