I need some help to diagnose what is wrong with my IROC. The problem is that when I am at WOT at anytime after about 4000RPM the car will backfire, immediate loss of power and the SES light will flash (not retain a code). For a little background on the car it's an 88 IROC with a 355, Trickflow heads, Ported Super Ram, LT4 Hot Cam, 1.6 Roller Tip rockers, and a 52mm throttle body. I have tried checking the timing (it's at 6 degrees), the EGR, the distributor is brand new, as well as the wires and plugs. I just am having a hard time finding the problem because it doesn't happen all the time. Also I have replaced the TPS and the IAC sensors on the throttle body and made sure to check the voltage of the TPS to be sure that it is sending the correct readings for idle and WOT. Any suggestions would be greatly appreciated!

I also posted this on the TPI board, but I know there is a great wealth of knowledge on this section of TGO. I would really appreciate the help to get this car outta the garage more and back on the road! - Plus it would be great to know my Thirdgen is still faster than my 4th Gen

 

Sorry to hear about your problem Randy.. Hopefully someone here will be able to help you out. Btw what chip are you using? What happend with those pics of your seats you were going to send..?

 

I wonder if you are needing a custom chip. It sounds to me like you may be going lean at wot.

 

Start with the fuel system. 4000rpm + backfire= lean.... running out of gas.

 

How long has it had this problem or is this a new problem?

The problem I was having with my car after the SR/AFR install was that is was running really lean at tip-in. Even after tuning it is still really lean at tip-in. You are still running the chip Kevin made for your old combo and are still in need of a custom chip, even more so with a ported SR.

Here a graph that shows my TPS, RPM, and AFR. I'm still experimenting with it when I have the time, which hasn't been too much latey...

 

You replaced the fuel pump too, right? Is the ignition module in the distributor new too? Have you run a scan tool on it to see what its doing when this problem happens?

 

I have a fuel pressure gauge in the car, that I honestly have to revisit and see if it happens to indicate that the fuel rail is losing fuel pressure at WOT. I have replaced the fuel pump twice now, both times with a Walbro 255lph unit. I unfortunately don't have a scan tool that I can place on the car that will help indicate any trouble areas. Any suggestions to help me isolate what may be causing this lean condition? Also I have an Air Fuel Ratio gauge in the car that usually remains at Stotich (sp) rather than Rich or Lean - but again I know it's not highly accurate but I was hoping it would show me if I was running either completely rich or lean. Thanks again, everyone!

 

Randy,
The AFR gauge should help indicate what the fuel condition is like when the problem occurs. I'm assuming you have the Auto Meter gauge with the red/yellow/green LED display?

Under normal conditions the lights should bounce back and forth between lean (red) and stoich (yellow). At WOT the gauge should go green and stay there.

The next time the problem occurs, try to catch a glimpse of the gauge. If your car is going lean at WOT, the gauge shop drop from green to red.

 

Thanks for all the response to this post. I will make sure to take along a passenger the next time I am 'unroot' the IROC from the garage and take her for a spin. Hopefully between the fuel pressure gauge and the air fuel ratio guage I will be able to figure something out. Thanks again everyone, and keep the suggestions comming

 

you forgot to add that you have a custom chip burnt for your new combo so we'll se if its the fuel problem on sat

 

Looks to be all fixed thanks to paitence and troublshooting and the great aid of TealMan92 aka FuelPump93 lol!




This problem along with the notorious fuse popping problem appear to be fixed.

 

Well since your i-roc is fixed and my GTA is fixed I guess the onlything now is to offer the challenge march 20TH its on to all show down at Cali. Speedway to see who gets bragging rights
BRING IT ON!

 

Are you sure you want me to beat you with my 3rd gen too! Damn, you'll have two generations of defeat

 

Have you guys gotten any faster in you 3rd/4th gens?

Last time I saw you guys your 3rd gen were in the high 13's and you 4th gens in the low 14's.

 

Both of the LT1s are in the high 13s now and you probably were at the track the last time I actually ran the IROC. Honestly I am looking for a strong performance out of the IROC and just more consistent times then the last two times I got her to the track, I replaced the 58mm with the 52mm, I think that is going to help quite a bit. So does it mean if Rusty and I both get our 3rd gens to the track that is enough to rouse the Bluebunny out of retirement?

 

IIIIfff I'm ready by that time, I will take on that challenge.

 

I won't race my Z28 until I have the '56 back up and running. Vetween the glass-jaw clutches (replaced another one last week ), my 10-bolt rear that whines-more-than-vincent-after-getting-spanked, and my now overly taught suspension (think: stiff but perfect at 120 MPH), I'm not sure how well my car will do now.

HOWEVER, when I do take it out for retirement it may only be for one race...and the other slot is reserved for Vincent and his ill-fated ego

 

So what is the current status of the truck? Seems you are just too hard on trannies, you said you blew up several 700Rs and now your T-56's clutches also can't hold up? "Granny shiften, not double clutchen..."

 

"...letting Mike drive too much."

 

I have to finish installing/trimming/mounting the EFI harness and then get a new fuel tank and fuel delivery system. So I won't be racing until summer.

As for my clutches don't last....It's because I need lower gears

 

When is that going to be? I can't promise to keep the IROC running for long

 

Likey story, I'd go with Bret's reason for the Z28
And go with the original manufactorer blame on the truck

P.S. Even though I know that now there are barely any original F*rd parts left

 

She just wants to be driven thats all she screams " drive me big boy drive me"

 

 

I bet the truck could take out you "Pink Rocket" as well as Rusty's "friedbird"

 

How much you willing to bet?

BTW - It's not the pink rocket rather the Pink Problem

 

I'm curious, what did you "teach" your suspension? lol I always find it funny to assign intelligence to inanimate objects. "Taut" would be more like it.

Lon

 

Nope. I meant "taught"....as in the past tense of "tiiiiiiiite"