Anyways, I just sold this TII-swapped Rx7 to a local guy who had never owned an Rx7 before--much less a stripped down, freshly rebuild Turbo Rx7... Anyways, he called me the next day basically unable to deal with it, so I offered to take it back and reinstall the thermowax and the BAC for him, as well as a different UIM without the TB-mod done to it--basically anything to make it easier on the guy while he was getting used to it.

Upon meeting the guy, I started the car and it seemed pretty flooded but it was able to hold a (hot) idle after about 5-10 seconds, at a semi-low 600 RPM's. Anyways, I drove it out of there, and everything was normal--smooth cruising, decent idle etc. However, several minutes later, and (ironically) as I entered the rush-hour traffic on the freeway, the car basically started to idle like it wanted to die, and began popping like crazy. As I revved the engine to prevent it from dying, it shook A LOT in the lower RPM's, and basically felt like it was running on one rotor when I would rev it up... Anyone who's experienced severe coolant seal problems knows this "one rotor" feeling (different than the severity of apex-seal failure). Anyways, it started bucking and popping at light cruise and I had to 'heel-toe' to prevent the car from dying as I was in stop and go traffic.

Since it didn't go away (like a severely flooded engine would after about a minute or two MAX), I got off at the next exit, where I popped off the IC to get a good look at everything... Everything was installed, so not knowing what to do--I raised the idle just to help get me back home.

As I drove out of there, the problem persisted with the popping, shuddering, inconsistent rev and bad/jerky response for nearly 10 minutes--and even with the significantly raised idle, it was still hovering just below 1000RPM's, just trying to hang on.

HOWEVER, several minutes later as I was coming to a stop, the idle only dropped to 1700 RPM's and the car began basically purring like a kitten. :frown: Seriously confused (since I was 90% sure that the engine HAD to be blown), I continued driving, only to find that yes, magically, everything that had been wrong was no longer wrong! Strong idle, smooth acceleration, no more popping... I drove the car confidently for around 20 minutes, and it's like the whole 15 minute "blown engine" fiasco had never happened! I checked the compression first thing when I got home, and it was a solid (hot) 95psi all around, with 150 miles on the fresh engine.

Anyways, anyone have a clue what this could be? I'm guessing that the old 550 primaries in there might be really sticky, and actually "stuck" open for those 15 minutes of driving hell? Who knows... Then again, that's why I ask.

Suggestions anyone?

 

Go with the gremlin theory. Sometimes the good fairy gets rid of them.

 

stuck injector, dead plug, dead wire, dead coil.

 

what do the injector clips look like?? maybe ones loose or broke?? even the pins in them??

 

Alright guys, it just did it again...

I've been working on this car all morning--installing the UIM with no TB-mod, installing a good thermowax assy. and a good BAC. I've been just tuning it--trying to get it perfect for this guy...

Anyways, I was just wrapping up after being fully successful. Rock solid idle, good BAC compensation, dead-nuts timing and TPS etc.

Well, as I was pulling out of my driveway for the "final" test-drive the car completely lost power and began running like the engine was blown... This time it seemed even WORSE then before. The engine died, and I quickly started it back up and limped it back down to my house, trying my best to keep it alive...

I was kind of freaking out because it seriously felt like the engine was blown... I popped the hood, ran and got my compression tester and tested the compression... It was FINE! Some fuel-smoke came out initially, but it was good.

Now I'm pissed.

Anyways, since it's obvious that there's either a lack of consistent spark OR too MUCH fuel (not too little), I think I'm going to replace the coils and wires first (because that's the easiest). Then if that doesn't work, I'll go ahead and pull the UIM and remove the injectors for cleaning, and replace the thermosensor switch on the water-pump housing.

Thanks for the responses guys. At this point, any imput is much appreciated.

 

Also, what makes this problem weird, is the fact that WHATEVER IT IS, it keeps correcting itself... What could this possibly be?

 

Intermittent problems tend to be electrical, loose connection, broken wire, etc....

 

ive seen this problem, a couple times, One car ran perfect and the guy put a kn air filter on his car and some how damaged his air flow meter , the car would not start at all. He put a used one the car ran fine, but once a day it would go into a limp mode, for about ten minutes. This car had no issues like this before he put it on. and my car used to do it also , but i switched to a haltech . good luck
let us know what it was

 

I changed out the plug-wires, coils and plugs to diagnose the "spark" system--after installing each item seperately, I drove around the block several times and the "blown engine" symptoms persisted...

The next step was removing the "top" of the engine bay, to access the primary fuel injectors and the water-pump thermo-sensor. I replaced the thermo-sensor with a different (known working) sensor, and then swapped the primary injectors with another set of 550cc's. Upon removing the injectors I noticed that one of the upper rubber seals on the fuel-injector (the ribbed one) was nearly torn in half... Perhaps it was pinched on it's initial install, and just slowly *split* over the past 150 miles... Anyways, not taking any chances, I still swapped the injectors and then installed everything.

The car was extremely flooded on the first start, and I was still very, very skeptical about the problem being fixed--but after about 20 seconds of holding the idle around 1500 RPM's, I "free-revved" and the car was quick to respond--although still a bit rough. I backed it out of my drive-way and started driving it... Everything was normal again.

I have a feeling it *wasn't* the thermosensor, but was probably the torn rubber grommet... Either that, or it was in conjunction with some sticky primary injectors. How else would the engine be flooded so bad? Obviously that torn grommet will allow in some unmetered and very turbulent air--causing the terrible idle etc., but how does it explain all the "extra" fuel? I dunno, either way--that was my problem.

Thanks for the responses.

~Erik

 

w00t, good jorb!