Diagnostic tool for -94 TBI engine?

[westlake17]

I have a -94 Nautique with the TBI injected engine. Does anyone know where I can find a "real-time diagnostic tool" for that engine?
Software - Pt.# L190130
RS232 interface - Pt.# RT0075
PCM says parts discontinued...
I have experiance from using similar tools on my cars with OBDII and ALDL interface, and once you have used them, you can't live without them...

[nms1991]

RE: Diagnostic tool for -94 TBI engine?

The one I have no longer works as the diskette had gone bad but what do you need to diagnoise on the motor?

[westlake17]

RE: Diagnostic tool for -94 TBI engine?

My engine was running rich at idlespeed. I started with checking that the fuelpressure was right. Then I suspected the MAP-sensor and changed it along with the vacuumhoses. Still rich. Then I managed to measure the voltage from the TPS (tricky to do without some special connectors). Voltage was a bit high, so I adjusted the TPS to 0.53 V at idle, and now the idle is acceptable. (Still on the rich side, i think.) Troubleshooting would be much easier with the right tool. What happened to your diskette? No backup? Yellow_Flash_Colorz: Can the data not be restored?
Do you know what the differences are from the Holley Projection. Is the ECU totally different?

[DavidF]

RE: Diagnostic tool for -94 TBI engine?

Westlake17:

I have virtually the same engine (a 95) that I purchased last September and have not had a chance to start yet. How do you like the engine other than the problem you are having? Do you konw the rated HP? So how are people supposed to repair engine management problems if PCM discontinued some parts? What did they (PCM) say?

[nms1991]

RE: Diagnostic tool for -94 TBI engine?

Didn't use very much, mainly used multimeter and fuel pressure gauge to diagnose the problems. Very simple system to work on. Is your throttle arm on the cable side painted red? What is your engine running temp? DavidF my solution to no parts to fix the fuel injection system would to get the new digitial system from Holley and get a distributor from a Gt-40 and Tfi module and coil and use the holley harness and computer and reuse the fuel pumps on the engine.

[westlake17]

RE: Diagnostic tool for -94 TBI engine?

DavidF;

This will be my fifth summer with this boat. It has 1700 hours on the clock. The engine is rated 310hp according to the documents I got from the first owner. The engine is poweful and reliable. Minor problems has been a faulty starterrelay and an airleek in the rawwaterstrainer(filter) that made the temp go high at high speed, and this TPS setting. I can recommend buying the "PCM EFI training manual" Pt.# L190140, from www.skidim.com ($10.00). Mark Schneider at PCM told me to install a carburettor(!) if I couldn't figure out the problems with the injection. That made me even more stubborn to solve the problem.

nms1991;
My -94 has the closed cooling system since new, and is now running with a 160F thermostat. I have bought a new 170F not yet installed. The throttle arm is not red. I agree the TBI is quite easy to understand, I had great help from the training manual. SKIDIM can still supply parts like fuelpumps, regulatordiafragms, IAC-valve. I suspect lots of parts beeing Holley, if you just could identify them.

[nms1991]

RE: Diagnostic tool for -94 TBI engine?

All parts on the tbi unit are holley parts the map and baro sensors are gm units and the temp sensor is also a gm unit. In 1994 they did have a recall for the tbi unit for sticking injectors and the red throttle arm is to mark the tbi had been changed. I have worked on these motoras since they came out and nvere could get all hesitation and rich idle out of the engine. Sometimes it is easier to go with older technology to fix your problem than to try to repair or to modify.

[DavidF]

RE: Diagnostic tool for -94 TBI engine?

I just returned from the CC Owners Reunion in San Antonio and spoke with Jeff from CC about these engines. He confirmed that they (TBI) are Holley units and put out a rated 308 HP. He also said that when tuned properly, ran stronger than the GT-40 engines of later years due to increased flow rate. I think he said they flow about 750cfm.

I discussed with him that PCM does not support the TBI units any longer and he confirmed saying that the Holley parts should work fine if one was able to cross reference the parts.

Seems to me that if the units idled rich, the IAC could be adjusted to compensate. Is it not that simple? Also, would the user adjustable Holley ECM work? Also, the MAP (Manifold Absolute Pressure) sensor is the main sensor for fuel delivery mapping. If the MAP sensor fails, the system relies on the TPS to control fuel mapping as a backup. However, the TPS map is purposely calibrated richer to alert an astute operator of a problem. There is a second backup mode that will allow the engine to run, just barely, but I cannot remember what controls it.

[westlake17]

RE: Diagnostic tool for -94 TBI engine?

Did he mention anything about the diagnostic tool? I really would like to get a copy of that software (and the RS232 interface).

[nms1991]

RE: Diagnostic tool for -94 TBI engine?

Beleive it or not there was not much info that came from the diagnostic program thats why I only use a fuel gauge, multimeter and service boooklet to work on them.

[DavidF]

RE: Diagnostic tool for -94 TBI engine?

Sorry to bring back old posts.... I just started my '95 TBI engine last night for the first time since purchasing it last September. It fired right up, but idled and ran rich even after warm-up. So, given my above post, the first thing to change is the MAP and BARO sensors (GM units). Does anyone know the GM part number? I would bet the part is cheaper from a GM dealer than a CC dealer.

[DavidF]

RE: Diagnostic tool for -94 TBI engine?

Still doing research on the PCM/Holley TBI setup. Here is what I have learned (remember, I am trying to solve my rich running condition).

The system is basically 100% a Holley ProJection 4D(i), 900 CFM progressive system. The ECU gets input from MAP, BARO, TPS, CTS, DTS sensors. The main fuel delivery map is obtained from the MAP sensor, with the backup being the TPS. A rich run condition can be caused by one or more of the MAP, BARO, TPS or CTS sensors failing and by excessive fuel pressure. I also understand, after talking to several people, that the system idles rich period, always has, always will. The idle speed is controlled by the IAC which opens or closes (via a pintle?) a vacuum bypass port. The MAP sensor then adjusts injector pulses to compensate for the gain or loss in manifold pressure. So, the EEPROM needs to be rewritten to provide less fuel at idle for any given manifold pressure (way beyond my scope). It may also have to do with the four huge injectors and the giant throttle plates....

So, to fix my problem I have purchased a new BARO and MAP sensors (identical parts...GM P/N 16137039 or equivalent aftermarket units) and today I am going to purchase a CTS (coolant temperature sensor) from my local CC dealer. I cross referenced the Holley sensor (P/N 534-10) to a Borg Warner sensor at less than half the cost of the PCM unit, but I am a bit nervous to install for one main reason: The Holley CTS sensor, designed for cars, is set to turn the "choke" setting, via the ECU, off when the coolant temperature reaches 180 degress. FWIW, the CTS is just a switch for cold starting (causes extra injector pulses). Now, we all know that our PCM engines like to run at a normal temperature of between 160 and 180 degrees. So, I am afraid that the automotive CTS will stay "on" even after the engine has warmed and thereby cause it to run rich ALL the time (mostly noticable at idle). I am going on the assumption that PCM specified a CTS with a lower temperature set point...or at least I hope they did as this could be part of the chronic rich idle condition for the TBI setup. I plan to test the set point in a pot of boiling water once I have the new sensor. If it triggers at 180 degrees, then maybe a resistor or something else can be done to "fool" the ECU into turning the "choke" off sooner. But, if the ECU is looking for voltage or no voltage, I am not sure what to do.

After I replace the three sensors this evening, I will test. If still running rich, I will test the TPS sensor and adjust or replace as necessary...a faulty TPS can cause the rich run condition. It is interesting that most sensor failures manifest themselves via a rich condition. I guess better rich than lean to protect the engines and give the astute operator an indication that something is wrong.

I will also check fuel pressure to ensure it is not above 15psi at any time. I fear that my return fuel line connection to the tank (no fitting on my '93 tank) is causing a restriction that is thereby increasing fuel pressure. One thing that PCM apparantly specified on the Holley setup is a fuel pressure (Schraeder type) port on the TB unit...very handy and I believe not normally fitted to the automotive versions. The fuel pressure can be adjusted via an allen head screw in the middle of the pressure regulator fitted to the rear of the TB unit.

I know this was wordy, but maybe someone else will find it handy.

BTW, I thought/think the TPS voltage should be 0.63 volts at idle.

[nms1991]

RE: Diagnostic tool for -94 TBI engine?

DavidF PCM called for a tps voltage between .5 to .7 volts at idle. Accually the ect sensor is the same as a car(90s vintage tbi system on a truck) as all it does is vari the resistance to tell the computer what temp the engine is running at. If you do not have a return line to the fuel tank then the fuel pressure should be rising beyond what t6he system can handle and the injectors should shut down. All the PCM ford based throttle bodies run rich no matter what you do and they all have a inherant bog when you slap the throttle down quickly. There is a couple of ways to fix it and both are pricey and most may not want to do it. First way is to get the newer style of Holley Projection(700 cfm version) get a distributor, coil , TFI module and heat sink and install on the engine, modify electrical harnesss to interface with engine to holley system, reuse fuel pumps and fuel lines from original. The other way is to order a carb, fuel line,mechanical fuel pump, and the Protec retro fit kit(EMS to distributor) and install.

[DavidF]

RE: Diagnostic tool for -94 TBI engine?

I used the boat for the first time Saturday, and overall driveability and power were awesome. I had two problems that if fixed, I can live with a bit of a rich running engine. The two Problems:

1) Very bad idle quality. Inconsistent idle speed and inconsistant fuel mixture at idle...sometimes very rich, sometimes fine. I suspect a sticking IAC from sitting unused for over 10 months without fuel stabilizer. I plan to remove the IAC and try to clean.
2) Although smooth and strong acceleration, once the throttle was stationary, the engine stumbled badly. I suspect the TPS. I am leaning away from ignition issues since the engine pulled clean and strong while accelerating. Just poor steady throttle state.

Things I have noticed. Fuel injectors have uniform and steady spray pattern (all four are about the same). Moving the TPS by hand does change things at idle. Idle speed is high.

I have routed a fuel return line back to the tank via the vent fitting. The vent is "tee'd" off the fitting with the return fuel getting the straight shot. I suppose this could lead to tank pressurization, but doubtful.

I checked the fuel pressure at it was about 18-19 psi at idle. I adjusted down to 15-15.5 psi at idle, but could not get it lower.

Would a faulty TPS cause the systems I am experiencing?

[DavidF]

RE: Diagnostic tool for -94 TBI engine?

Ok, so I thouroughly tested the TPS and IAC motor. TPS works properly, but need adjustment from .43 volts at idle to .53 volts at idle. Voltage now measures slight above 4.5 volts at WOT which is within Holley (PCM?) spec.

IAC motor was non-functional and basically causing a massive vacuum leak at the throttle body. Placing my finger over the air hole, caused the idle to drop to 500 rpm (expected, 700 is normal with functional IAC) and the fuel injectors to deliver way less fuel and the rich condition dropped off significantly. Releasing finger caused idle to jump back up to 1100 rpms. Removed IAC and pintle was not extended. I believe normal behavior is that the pintle retracts on key on, to reset itself and then extends to maintain idle (hence normal brief fast idle upon start-up). I forced the pintle out and got it to work sporadically. The part number on the OEM IAC indicates a Chrysler unit that I cross referenced and was able to purchase at the auto parts store.

Will test tonight and report.