Good evening folks, Merry Christmas!

I'm about to purchase a '97 SST (2wd w/ Magnum 360) with just north of 150k, and I'm getting it at an absolute STEAL because the owner's fed up with the trucks ability to clean out his wallet. Anyway, I'll quit the foreplay and we'll dig right in.

Symptoms: On the first "key-turn" of the day, the engine will crank 3-4 times and fire right up. No drop in RPMs, will sit at idle and purr like the kitten she was meant to be. HOWEVER - once she's been idling for a few minutes, getting warmed up for the dance about to take place, if you blip the throttle she turns into a narcoleptic and falls flat on her face. After this happens, she'll show you no love for hours. She cranks and cranks, but there's no firing her cylinder walls up for basically the rest of the day.

I'm very familiar with the classic beauties, but this "new-fangled" electronically controlled business has yet to be my strong suit.

I've been searching for hours, only to find issues that faintly resemble my predicament. I'm not sure if the plenum gasket has been replaced, but the catalytic converter is a newer high-flow unit (I'm told). He also said he did a standard tune-up hoping it would help (which in my book is cap, rotor, plugs and wires, and air filter), and no plugs looked to be in bad shape.

Can one of you help me out before this very attractive pickup files domestic violence charges against me?

Many thanks in advance, and if you need to ask a question to give a better answer, please do so!

 

Maybe it is because I work in this field...... But ifind absolutely no humor in jokes about domestic violence orchid abuse........

But here is my 2 cents. First I would suggest downloading service manual from FAQ/DIY section. Then find the sections that show how to check the TPS and clean the IAC. If cat was replaced I suspect plenum was or is blown. Verify that and probably need to replace O2 sensor (upstream).

Also if none of these help I would check fuel pressure and then crank sensor.

Also check for TSB for plug wire routing. This appears to cause problems for these engines.

I know that is a pretty good list but several problems manifest with similar symptoms.

 

I'm against orchid abuse as well, so I'm glad we're on the same level... No seriously, I meant no offense.

Fair enough, I'll pull the IACV and clean it just to be safe, and take a look the plenum gasket with my handy dandy mirror and flashlight technique. I would usually associate a bad TPS with stuttering acceleration and this supposedly doesn't fit that description, but while I'm digging around I suppose it won't hurt to check.

Thanks for the feedback gdstock, and for keeping the new guy's humor in check.

 

I probably came down a little hard. Sorry about that as I just finished a DV fatality case just after Thanksgiving. I find it difficult to "be off work" sometimes.

Based on your symptoms there may be a couple of things wrong and previous owner may have been victim to someone throwing parts at the problem without a good diagnosis being done. Unless it was done by a dealership I have found that a number of reputable mechanics don't even know about plenum issue and a clogged cat is a typical symptom. On my Ram the po replaced cat but did not go farther so plenum was in pretty bad shape. Many change parts without really testing them and then get frustrated by cost and still having issues. Iam surprised by the number that want to change PCM when they cannot find anything else. It usually ends up being a combination of problems. Service manual gives test procedures. IAC usually needs a good cleaning. Do not turn pintle as this will damage it.

The person selling it - his frustration may be your gain. Mine was in bad shape and after fixing problems and neglect it runs great.

Welcome to DF. Lots of good info available here and lots of people willing to help out.

 

Nothing to worry about gdstock, we all bring our work home with us and if I had your job, well let's just say you probably exercise much more self control than I would in the situations you've encountered.

He did say the shop put a new PCM in the truck and it showed no change. You're good!

Turns out I won't be doing this work myself after all, my son just had a mishap last night on the way to his apartment so I'll be working on getting that back on the road instead of working on this project. Oh, the joys of parenting. I get to work on the '55 Ford we built for him, while he works on putting love stains in the upholstery of my Bel-Air.

Do you have any estimate of what a shop would charge if this plenum gasket were the culprit?

 

Around 6 hours labor, and, if done 'right', about 100 in parts. JUST for the plenum problem. That doesn't include changing plugs, O2 sensors, or the cat. (if necessary.)

 

And broken intake bolts.

 

Which, as I have found, is inevitable. lol

 

I've only done about ten of them over the years, and only lucked out on my 2000. My 98 had 3 broken bolts. And the others I've done for/with people had at least one. And of course that ONE always has to be the passenger rear bolt.

 

I broke the front two....... Ended up having to drill thru them, then blow out the remainder with a torch. At least they were open holes, that DIDN'T drop slag INTO the engine.