Stops at 4000 RPM, CEL, found 4 EEC codes, need advice

[Orkin]

My recently purchased '94 ATX has started running kinda of rough, with a general loss of power, and the CEL comes on sometimes, but the most troubling problem is that I can't get it over 4000 RPM. At 4000, it starts surging, and running very roughly

I wiped the EEC codes, drove it normally for a day, and then checked them (KOEO only) and got: 172, 176, 332, and 335.

I searched around here and found that the 332 is most likely caused by clogged EGR passages, and I did find that the nostrils are clogged, but haven't had time to clean them yet. Would 335 (DPFE voltage out of range) mean I need a new DPFE?

With 172 and 176 it looks like I have a vacuum leak. Could that be what's causing the problems at 4k RPM? And how would I go about finding the leak?

Thanks for any suggestions!

 

[sdpatt]

Welcome. If the rough running problem starts at exactly 3,950 rpm, then the problem may be a vacuum leak related to the secondary intake runner actuation system. Here is the link for the hose routing of that system. It sounds like the engine may have been victimized by a misguided maintenance operation by a previous owner. A good search for other vacuum leaks around the intake manifold might prove informative.

 

[Orkin]

I checked around for vacuum leaks, following the info you gave, and generally looking around, and couldn't find anything except for this one questionable hose, that I'm having trouble identifying:


And also a hissing sound coming from this area (to the left and behind the engine), but it's too cramped to tell exactly where it's coming from without further investigation:


Is it possible that instead of a vacuum leak, it's a problem with my fuel system or engine control causing the lean condition?

I also noticed a chirping sound coming from somewhere near the front of the engine today, any idea what this could be?

 

[Slo-Sho]

That is a coolant hose going to the heater core, not sure on flow direction. Have you checked the IMRC (int. man. runner ctrl.) vacuum reserve canister for signs of damage or cracks? With the engine off I would plug the vacuum source for the IMRC, you should have full power from 4k to redline if this is the cause.

 

[AutoSHO]

You didn't get a code for a transmission sensor? I would have guessed with an ATX and it stopping directly at 4,000 that it was the neutral rev limiter kicking in.