So I put my engine back together with Maxbored TB from 75 to 82.5mm, installed port matched intake elbow and ported and polished intake manifolds. The injectors came out, but after 3 weeks the local place said they cannot get the correct adapters to clean them, so they were put back in without being touched while they were out.

Problem: Engine failsafe mode
When I first started it up, the pedal was floored by itself and the car was hitting the 2500ish rev limiter, then down to a severely missing idle, then almost dying, then back to 2000 rpm.

no codes....


Any and all help will be appreciated

 

Mine did a similar thing recently when I was messing with the cable adjustment and disconnected the battery. Don't remember if I had the Fail Safe mode though.

It sorted itself after a restart or two.

Did you plug in all the connectors to the TB?

 

Everything was plugged in. the gas pedal was to the floor all by itself at first without tension on the cable, so I took off and re-installed the throttle cable again, same effect.

I restarted a dozen times, it was barely able to stay running long enough to warm up and was missing very badly the entire time.

I may just take everything off and check to make sure I didn't forget to plug in one injector or something obvious (other than the TB) and try again.
After having a quick look at my wife's xj8, i see the TB is different, so no easy testing by swapping TBs.

This will get fixed of course, but may take some time. Resistance is futile, the mods will continue

 

If it was the throttle position sensor, would that have thrown a code or not?

 

Do you get the engine fail safe immidiately when you turn on the ignition (but no start)? Also very odd that you can't read any codes, not normal for an engine failsafe condition. It sounds as if the throttle motor isn't connected, but that would throw a code. You can check this by looking at the butterfly when you turn on the ignition, the butterfly should quickly close then. Also check when you floor the pedal that the butterfly opens accordingly.

 

I got the ABS/trac not available, then tried to start it before seeing any other warnings....so unfortunately that opportunity is lost.

I know I did violate the cardinal rule of only changing one thing at a time by taking more than just the TB off, so I'll keep trying whatever is recommended until we succeed.

I will try looking at the butterfly upon key on tomorrow morning and report back.

 

Incorrect install of the TPS has the same effect, ie the ecu will cut of power to the throttle moter, this might be more likely actually.

 

The sensor was left on the TB in this case. I only took off the other end with the throttle cable. I will make some time tomorrow to re-install the TB (after jb welding a loose push in coolant tube) and have a look at the butterfly to see if it corresponds to pedal movement and report back.

 

It's sounds like the ecu attempted to re-calibrate the TB with an injector off.

Time to go back over your install and check coil/injector connections.

The only difference between your wife's TB and yours is the air assist. You can adapt the XJ8 TB to SC application by changing one part, all is revealed when you have them next to each other. But at this point I'd not try this, confirming all is plugged in before swapping TB's.

So once the work has been double checked as 100% plugged in (with the battery disconnected) go for a start and let the ECU/TB do their recalibration, it is as you describe, rev's immediately climb then drop down to almost stall as the ecu finds the idle point (a clean MAF also aids this learning process) then climbs back to happy idle point, let it run for 10 minutes to store the new values...I MEAN EVERYTHING PLUGGED INC INDUCTION TUBE/MAF IN AND DO NOT TOUCH THE THROTTLE PEDAL

What you have done is changed the amount of air flow into the engine, and the ecu is working with old values, it's attempting to re-evalute this new amount of air and adjust fuel, throttle position and other values to the new values. Simple really, but can cause alarm if not witnessed before...

 

Yes this definitely caused some alarm.

what do you mean by clean MAF?

One thing worth mentioning is that the gas pedal movement feels like it now has a lot of resistance, like the cables are now not lubed well <-- is this a clue of anything?

given how bad it was missing, I am thinking maybe an injector is not firing, so I'll tear it down and have a look after trying only the TB re-install again.

 

I would look to see if you have an air leak, possible injector seal??

 

To clean the MAF sensors you need a can of electrical contact cleaner, not wd40. Remove the sensor from the induction tube and flood the cleaner onto the 3 sensors and let the fluid evaporate fully before returning it to the housing.

A tight throttle cable means it's not routed correctly, or installed correctly - don't bother TB re-install, just get to the misfire first or you're likely chasing your tail as it'll be groundhog day...

Sounds like you rushed getting it back together. Any codes to report?

 

You could also remove the throttle cable from the TB to remove that from the list of possible reasons. (binding, too tight etc.)

 

I did rush it back together on the TB cable re-install.

I noticed the butterfly had to be manually rotated a small amount for the throttle cable assembly to drop back into the TB with the screw holes lining up, is this correct, or did I make some mistake here when assembling that part?

No codes

I have electrical contact cleaner and will clean the MAF before trying again.

 

Do you mean start it up without the cable attached?

 

Install the TB BEFORE attaching the cable

 

I personally have not had to do TB replacement yet, but would a Hard Reset be appropriate at this point so that the ECU can start from scratch? Others will know better than me, I just wanted to throw this in.

 

yes I did install the cable after the tb was bolted down.

I may try starting it up without the cable attached, just to remove the possibility of the cable being any issues.

 

When I put my car back together with the stock stuff cleaned up it took a hard reset and it worked that way.

 

So, to clarify, you put everything back together with no mods (no porting, etc) and it ran like mine did? Missing really bad like maybe an injector was not plugged in bad?

If I do a hard reset, would I loose my tune? (puffing out lower lip, pouting)

Lastly, HOW do I do a hard reset.....I've never done this before...