I have an L98 engine installed in a 76 FJ40 and I'm having issues with it dying when slowing to a stop or going around corners. I've replaced the throttle position sensor and idle control and a few other things. The guy I bought it from said he had the fuel injectors replaced and went a size larger. My mechanic thinks its a programming issue but the dyno shop I took it too said the L98 is older tech and they can't tune it. It has a very strong exhaust smell when running, I'm thinking to much fuel but I hope I can program to this and not replace injectors. Does anyone have any shop or tuner recommendations? Or any ideas of what I should do?

 

This will be a tough one since the engine is a transplant. It sounds like you had no part in the transplant into your FJ? I would tend to agree with your dyno guy that this sounds like a tuning issue. So there are a few ways I would go if this were my truck. Optoin 1 would be to buy a set of stock injectors and hope that fixes the tuning issue. Who knows what else was changed when the system was turned into a stand alone. Option 2 would be a new tune. These older computers require a prom to be burned to change the tune. It is old tech and hard to find someone that will do it or even has the equipment and can get expensive. I would recommend contacting Bob over at Dynamic EFI ( www.https://www.dynamicefi.com) he is a great guy and their replacement computer for the older EFI stuff is killer. I put one in my 86 Corvette and now I can tune and flash with a laptop just like the newer cars. The EBL Flash product he sells has great support on forums especially in the Camaro and Firebird groups. Bob is also a big help directly as well. He was very patient with me when I got my EBL and was trying to figure out how to get started on my first tune. In the long run you will have a better running engine cheaper by buying the EBL Flash rather then throwing parts and proms at what you have and hoping for the best.

 

Thanks for the info. I wasn't involved in the build and the guy I bought if from isn't getting back to me. I'll reach out to Bob.

 

My first thought does the conversion have a functional Vehicle Speed Sensor (VSS) that's talking to the ECM? This would definitely cause the stalling upon decel and approaching a stop.

Do you know if the engine is completely stock with no other modifications aside from the larger injectors? I'm thinking you could get away with an adjustable fuel pressure regulator and turn the fuel pressure down. I would still like to know how the engine is running so it helps if you have some means of scanning the data. Adjust fuel pressure until you can read at least a stoic idle then see how it does on a drive followed by flogging it. https://witchhunter.com/injectorcalc1.php

Which computer do you have? 1227727 or 1227730? Both are purdy much the same except the 1st one mentioned is the under hood version that the C4s got. Make sure you mention that to Bob as the connectors are different on that particular ECM.

 

Define larger injectors. From 22 to 24, probably ok. 22 to 36, probably not.

 

Not sure, the guy a bought it from said one size larger so I assumed 24.

 

This goes way above my knowledge of engines. The shop said he thought the VSS was hooked up. As far as I know the engine is stock, with the exception of a cold air intake and MSD coil and wires and the larger injectors but the guy I bought it from isn't returning texts. The engine runs great until I start to slow for a stop but there is a very strong exhaust smell all the time. My mechanic said its not throwing any codes when he does a scan. I'll have to ask about the computer. Bob emailed me back and asked about the VSS and then asked what computer I have.

 

Wouldn't a bad VSS give you a bad signal and speedometer reading?

 

Well your guess would be as good as mine since we really don't know anything. I just know that my new to me C4 when purchased didn't have the VSS connected and stalled every time upon decel to a stop. It would do the same rounding a corner, if I didn't release the clutch quick enough during the down shift. Since this is a FJ conversion, for all we know, the VSS could be connected directly to the FJs speedo and nothing to the ECM. At least we know the engine is allegedly stock so I'd venture to say PROM tuning is not the problem. IAC was changed but was minimum idle set correctly? TPS changed but as long as the volts aren't way out of spec I don't think it's an issue. Mines set at .73 and I never cared to adjust it lower. This is more of a question to the forum, what does the absence of an IAT do or if it's laying there on the intake since you mentioned no cold air intake ducting. Have you located the ECM? If the outer casing is black plastic with four connectors then it's the 1227727. If it's a metal case with 3 connectors then it's the 1227730. Another thing to note on conversions, do you have a functioning Park/Neutral switch? I was still running around with the P/N switch hooked up on my T56 convert and datalog indicated that even after checking manual transmission in the prom. I depinned it from the ECM and that didn't seem to make a difference with my stalling issue or the way the engine ran.