Recent content by steveC

So, finally have an OK IM147 test report in my hand. Since the last update, I'd installed a new NTK 23023 O2 sensor plus a new manifold/downpipe donut. The NTK sensor does switch quite a bit faster, but still seemed to show it trying to run a bit on the rich side. Results (remember, this is the...

FWIW, the FSM specs no more than a 20psi drop in fuel pressure after being shut down for 30 minutes. Thus, if you have the normal 31psi idle fuel pressure, it should be at least 11psi 30 minutes after shutting down. (My experience is that it raises to 35-38psi if the motor is hot due to...

Hmmm, I think we're saying the same thing, really. I stated it poorly. I'm referring to RPM as a proxy for a "timed intake stroke". If we know what each intake stroke displaces, and the pressure/temperature of the air feeding it, then we can derive the amount of oxygen in the mass of each...

Offhand, it sounds a little like it might have flooded. After it sat awhile and the excess fuel evaporated, then it started OK. It's happened to mine a couple of times in the 12 years I've had it, usually in cooler weather when it stumbled and quit after the first try. TPS sensors show up under...

Could be. I was always under the impression that RPM was part of the equation to know how much mass airflow was moving through the engine (combine it with manifold pressure and temperature, and you can compute how much oxygen is available to match up to hydrocarbons). But, heck, I've never...

....aaaand that table didn't render right at all. Note that the Delphi spec numbers are all even increments of 5kPa, and that should help you see it. Damn...

My understanding of it is that the sensor does report absolute pressure, ergo "(M)anifold (A)bsolute (P)ressure". It uses this, plus TPS and RPM data to calculate mass airflow into the manifold (it also uses the IAT data to add a density factor). Corrections for altitude + weather variations are...

I'll second what EcoMike says here...at least the early Mopar MPI setups (the one I'm familiar with) appears to use the GM-style "one bar" sensor. This is pretty common on a wide range of non-boosted engines. (There is also a 2 and 3 bar variation of the same sensor for engines with boosted...

Interesting data point... This afternoon, before doing other things, I went ahead and washed the throttle body out and ran some Seafoam down the intake for awhile, in an attempt to try and clean some carbon out. Took awhile, it sat and idled much of the time, and warmed up quite a bit in the...

I lied earlier. Remember, this is a 1994 HO setup, Mopar MPI, not Renix ECU *signal* ground ties to the right rear of the block, along with power. ECU *sensor* ground doesn't appear to actually take a body ground anywhere according to the schematics. TransControl, CamPS, speed, TPS, ECT, AIT...

I've run it through a couple of years ago, not recently, however. That's on my list of stuff to try, although I have my doubts about it being a solution. (I say this, because the throttle response suggests to me that it's a little lean, yet the O2 sensor is cycling...just seems to be doing it...

The permanent gauge isn't a bad idea at all. I have a shop gauge on a hose, but I don't exactly want to leave that on and drive any distance, and it's a pain to connect one to a hot motor. The pressure tests fine sitting in the shop from a cold start, but I've often wondered if it stays in spec...

Bumping an old thread, forgive me. My 94 4.0 HO is currently failing the AZ NoX test (required every 2 years). 2 years ago, it failed the NoX, at about 228K miles on the clock. First time it had failed in the 10 years we've had it. At the time, I suspected old injectors not flowing well, and...

Ah, there was a *reason* for that; they wanted a platform that appealed to SJ buyers (which were notably well off, and were consistent, high-margin customers), but that was light and efficient enough to get decent mileage and smog numbers, and would be affordable to produce, and flexible enough...

This is interesting. I've seen other threads about "which year is best", etc. Here's a different question in the same vein: If you wanted to "resurrect" an XJ into near-new condition, mostly stock, but with some performance/driveability/wearability/appearance improvements, which year would you...