Hello all, my son just graduated high school and turned 18 a few months ago. He dying to join the high performance V8 world. We picked up a 1994 formula 5.7 LT1 4 speed auto.

I want to teach him but I need to also learn. It’s not in perfect shape.

I’m and old school small block Holley TH350 guy. Got a 72 nova 383 stroker Im building slowly, but I want him to learn about and have the benefits of injection, overdrive, and lock up. LS cars out of his price range.

Can anyone advise if the MAF looks right? Seems aftermarket and the wiring appears redone. Af if the previous owner attempted to use an aftermarket unit or MAF from a different car. It does not seem to match. Do I need to reverse this? Should their be a tune to support this? Could it be putting the car in limp mode, no SES light. Engine runs strong.

 

It just looks like the pigtail was replaced (maybe because of damage). Pigtails often fit multiple vehicles, so wire color matching is not usually maintained. The MAF is installed in the correct flow direction according to the arrow on it.

 

Thank you. We are new to the whole OBD1 LT1/4L60 world. We been chasing a constant limp mode issue. Transmission stays in 3rd and allows only manual second.

No SES light.
trans rebuilt 2 months ago including solenoids.
new ignition switch
new ECM 2 years ago

 

That pigtail is trash. In any 5V system (MAF) you need really good soldered connections. The resistance increase in those crimp connectors can lead to all your problems. My son's step dad helped him replace an alternator in his Focus. Ford makes several versions. They got the wrong version and got the correct pigtail for it. He and his stepdad cut the wires and used crimp connectors. Well the added resistance messed up the voltage regulation and it burned up quickly. You need to get a new pigtail and do it right or you MAF signal to the ECU will never be right.

Even if those are the newer solder and shrink connectors, the job still looks subpar. I would get out an old fashioned soldering iron and old school heat shrink and do it properly. This is pretty significant wiring harness repair needed at this point.

 

Exactly why I posted here. Thank you. I have an old soldering gun, heat shrink, and solder.

That will be the next thing I do.

Do you think that’s the reason I’m going into limp mode?

Any reason why these cars have both MAP and MAF?

 

Unlike gen 1 SBC like your 72 Nova, these computer controlled cars you need to be able to scan them to see what is going on. SCAN9495 reportedly is a very useful, free download, but you do need to buy a specific cable to plug into the port on car and a laptop

 

yeah brother, I’m an old carb guy I fix myself, and my daily driver is a newer car I would just drop off at the dealership if it had issues. This car is in the middle era I’m not used to. I’ve scanned and fixed simple OBD2 issues on newer cars, but not used to this middle 90’s era. This is for me to help my son learn to care for an older car.

check this out. I think the last owner was chasing this same issue. Feels like a transmission issue at first glance. He had the transmission rebuilt 2 months ago. The brain to years ago and the ignition switch, which is known to cause issues, a few months ago. I think we are almost there.

im not sure if this is limp mode or a bad trans solenoid or a sensor issue. I don’t have a scanner and no local parts house scans OBD1. Taking it to a reputable shop on Wednesday. I just hope they actually scan the car and not recommend major repairs on a knee jerk reaction instead of really investigating.

I tried to pull codes via the old paper clip method but all’s that does it turn on the radiator fans and the CEL stays on. No blinks.

 

93 was the last year you could blink codes on these particular cars. If you are going to do your own work, you need a scanning solution (tool or software/laptop). Trans codes don't often cause SES lights.

MAP and MAF are used for better engine fueling control. Those solder sleeves might look a little ugly, but if they were done correctly, they should be fine IMO. This is where scan data would tell you if the MAF was working ok.

 

yeah, I don’t know enough to do it myself. Taking it to a shop Wednesday. I just hope they don’t assume it’s a bad transmission and just say to have it rebuilt. It was rebuilt 2 months ago.

 

Go ahead and snag yourself a ALDL cable to usb. Get a cheap laptop and download scan 9495. TunerPro also has a live data feature, but I personally haven't used it yet. I think this is the correct cable you will need but get under the dash and count the slots in the port.

http://aldlcable.com/products/aldlobd1u.asp

There are 2 different set ups. The 95 used a obd1.5 in theory. It has the 16 pin obd2 port with obd1 brain behind it.

http://aldlcable.com/aldl.asp

Pull the negative battery cable off for 15-30 mins and reattach, see if "limp mode" goes away?

 

thanks for the info on the years of the vehicle! A assumed the ECU was fried or something.

 

you will have a much shorter path chasing your tail if you do get something that can scan the car. SCAN9495 has been suggested. Just google it. Its free. Gary Doug published it on another forum

You also "may" have a modified aftermarket program that supports some mods that may have been done to the car. If a dealership get ahold of your car and dumps the stock tune in it....you will have issues and the dealership will not be able to "restore" your aftermarket tune

This is why it is strongly recommended you obtain the ability to scan & log wtf your PCM is seeing

 

Thanks brother. Awesome resource. Just need the cable and that’s it. Thanks for the info and advice.

 

3rd gear start/ limp mode with no SES light is typical for transmission codes on a 94. Ask me how I know. One of the biggest mistakes made is putting a rebuilt trans in the car or an off the shelf replacement and getting the wrong rebuild or trans. I worked on a 94 A4 some years ago and after lengthy troubleshooting discovered the previous owner had installed a 95 trans in a 94 car. 3rd gear start/ limp mode/ no SES. Silent DTC 84 set. The cure for that was to load 95 code in the PCM and run a wire from PCM to the extra pin added in 95 for the PWM solenoid (94 doesn't have it, simple on/ off TCC lockup apply strategy, while 95 uses the first gen rudimentary pulse width modulation TCC lockup apply strategy). 95 and up will have "PWM" in raised letters on the pump housing. 94 does not. Code 84 is kind of misleading in this scenario because it refers to the 3-2 downshift solenoid voltage too high or low for > x seconds. 94 PCM code lacks the programming to describe a problem stemming from an additional solenoid it doesn't know exists. PCM pin D6 (blue connector) feeds ground to pin U on the trans case connector on a 95 trans with PWM solenoid. The 94 case connector is missing that pin, while the electrical harness inside the 95 trans has the ground and power wires for the PWM solenoid. That's the only electrical difference between the 94 and 95 engine harness; that one wire. And the 95 PCM code has the programming to control it. Both 94 and 95 use the same 16188051 PCM, so it can be flashed with code from either year. I was fortunate, the car I worked on had only been driven a few hundred miles before the PO cooked the engine. What driving it in limp mode will do in a short time is cause significant wear to the 3-4 linings and the lining in the torque converter. Still, a few hundred miles probably equated to about 20,000+ miles of wear on the linings. If you've been in the pan on this trans, or have any pics of the trans before it went in, see if you see PWM on the pump housing or if the valve body matches 94 or 95 (reference: https://www.sonnax.com/tech_resource...fication-guide ).

I ultimately replaced the internal harness with a 95 version that tested good, all solenoids tested manually on the bench, ran the wire from D6 to U and flashed in 95 code (.bin file) and added back changes I'd made for the headers/ O2 relocation, etc.

EDIT: Also need to check the resistance of each of the solenoids against the reference specs from the Sonnax link above...

 

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Wow! Awesome info! Thank you. Most of this is above my capabilities. We ended up taking it to a reputable GM shop. My problem is I hope they find the problems and not just start swapping parts. Then end up with a bill for a new ECU, sensor, a referral to a trans shop, and still have all the problem.

Thanks for this education on the inter workings. I’m wanting my son to learn about this car.


let me ask you this. Did your symptoms start the moment the incorrect rebuilt transmission was installed?

on my car, the original trans was rebuilt two months ago. It ran perfect until a week ago. It started the symptoms intermittently. Then got exponentially worst over about a few days time. Could this still be the issue you mentioned. Knowing what I just mentioned, what could it be?

 

The car I had came to me with a blown engine. When I drove it the first time, I could tell something was really off. There are some tricks trans builders can do to 'make it work' with the scenario I described but the life would be severely shortened. Hopefully, the first thing your GM shop will do is check for stored codes. I'd have specifically asked them to do that, and if any trans codes are present (pretty much a certainty) start troubleshooting the cause(s).

 

Thanks for the help man

 

Nice find! Good luck!

 

Took the car to a local reputable GM mechanic. Scanned it and got code for a bad B solenoid.
he changed both A and B and all is perfect.

the issue is that this transmission has been rebuild two months ago. I called the transmission shop that did the rebuild and he said that they replace all solenoids and he did not know what caused the bad solenoid. He said it could be a bad ignition switch. That was replaced 2 months ago as well.

hopefully this will not be a reoccurring issue.

Any underlying issues that cause premature solenoid failure? Line pressure issue maybe?

 

Glad you got it back up and running! Congrats! I'd still check the resistance across all those spliced wires on the MAF pigtail. I'd make sure across all those splices resistance is near zero. If it's not, I'd repair it.