New Engine doesn't run right.

F

Fred

NAXJA Member
NAXJA Member
Location
Colorado Springs, CO
Well, new engine doesn't seem to want to run right. It's cammed, but mildly according to the machine shop. It might be running lean, probably try a map adjuster. With the map sensor not working, it runs okay, some missing intermittently. The scan tool show rich while running with map not working. With the map working, it backfires badly at 2k rpm. It's bored .030, Hesco ROV cam, block and head decked minimally, HO head on a Renix block, some porting on the head, bored T-body, Mopar header with 2.5" exhaust(T-body really woke up the old, tired engine). I'll be at CO fest, but driving Flores's BMW. :)

It's in a 90, using the Renix system. Flores's scan tool doesn't show anything being wrong. The plugs are indexed, the cam was indexed at the machine shop, Flores says the distributor is indexed correctly.

And if it ever runs right, it's definitely pumping more air than the old, tired, stock engine. :)
 
I linked to your website, he says that's what he did. Was I there, no. Whatever the emoji is for who knows. I definitely tasked him on it, and it is not his first engine job.
 
Fred said:
I linked to your website, he says that's what he did. Was I there, no. Whatever the emoji is for who knows. I definitely tasked him on it, and it is not his first engine job.
Click to expand...

In that case check the TPS & MAP sensor.
 
19 lb injectors, with more displacement, bigger TB, headers, ported head, higher compression....no wonder it is running lean. A quick and dirty check is to swap to a stock TB and see if it runs richer/better. A map adjuster can only go so far, you most likely will need to step up a size on the injectors. The Renix ECU has a limited control range and will not compensate enough to make the 19lb injectors flow correctly. You might get by with a MAP adjuster, but either way, you need to keep a close eye on it while you are figuring this out. I recommend a WEGO AFR.

When I did my stroker about 15 years ago, AFR's weren't cheap, so I spent quite a bit of time on a dyno.
 
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The distributor was diddled with, and it does run better. It was really rough at around 3000 rpm, but I had put it on long arms previously without really checking pinion angle. Looked low, so I adjusted the upper arms over two days of fighting with it(I work in the parkway on a slanted driveway, makes things "interesting.") When I went to test drive it, it was deader than a doornail(what is a doornail?). Pulled off the positive leads and the lead to the starter relay showed 20 some ohms to ground. Not good for an unswitched lead. Pulled off the relay, it was fine. One of the connections on the post for the battery lead, with two green wires, was 20 some ohms to ground. Finally got the optima battery charged, put it back together without the questionable wires. Starts and runs, still seems rough around 3k rpm, but with considerable improvement. Definitely just a motor thing. I'll finish up the map adjuster I've been dilly-dallying around on constructing, and see if that helps.

I just have a hard time thinking anything is running lean at 6000 feet, even with improvements in air flow. Basically, the engine is running at 80% of sea level. When stock, while passing emissions, the plugs and tail pipe were always black. I'm using 19# 4-hole balanced injectors. When I first installed the bored T-body, it was the smoothest running 4.0 I'd ever heard, until it began it's downward spiral. Seems to me, I would have had to improve air flow about 30% to get to were the computer is trying to adjust to over 100%. It is flowing more air, base on exhaust noise, but 130%? Low end torque is okay, nothing impressive. revs freely to 4800. I know it's not broken in, but I was expecting a bit more. :)

If it is running lean, should I just put in 21# injectors, and forget about the map adjuster?
 
Don't do anything without getting measurements to know exactly what is happening. I really recommend an AFR gauge. If not, find a mechanic with an exhaust gas analyzer or take it to a dyno.

It is way too easy to burn up an engine.
 
I disconnected the vacuum to the fuel pressure regulator on the fuel rail. It did improve it, but far from perfect.
 
that should make it run richer.
 
Is it a new or rebuild distributor? I've gone through about 12 renix distributors in the last 5 years, and about half of them have been bad out of the box.
 
old_man said:
that should make it run richer.
Click to expand...

Yup, that was the idea.

Used distributor out of another engine. Too bad I sold the dist. I got from Mopar Performance lo these many years ago because I didn't think I'd use it. :)


Even with the enrichment of the fuel system, it's still not right. I've got 22# injectors to install, and I should have a map adjustor box done shortly. I'm not totally convinced on the lean running being the issue. Did I mention that the ignition system from the distributor out is all new with fancy plug wires, the only Renix with an after market coil thanks to a custom adapter made by a machinist friend, and indexed plugs? I know the ignition system doesn't make a whole of difference for the Renix, I've being playing with plugs and wires for the last 24 years with no noticeable change in mpg, but it has strange misses when it's cool, and at lower rpms.
 
22# injectors in. Better, still far from perfect. Definitely a change from the 19# mustang injectors with maximum fuel pressure all a the time. The idle dropped almost in half, had it set at about 800 rpm, now it's about 5-600 rpm after the computer adjusted. Fuel pressure adjustment didn't make much difference at idle. Driving ~13 miles including over 75, it ran well, seemed better off idle, but not as happy above 4k rpm. I had Zac test drive after the install, it sounded damn good. I drove it with the fuel pressure at max for the return. Had a little backfire at 2k rpm and cruising, but overall seemed a tad better. I guess I need to put the MAP adjuster box together. It's half done. Note, this engine is not even close to being broke in, still blowing oil at less than 150 miles.
 
I replaced the MAP sensor, and reset the TPS with the throttle plate just open. No idle, so I had to open the throttle plate to get an okay idle, just above 500 rpm. It's a really lumpy idle, but it runs pretty good after it's warmed up. It accelerates easily off of idle. It runs very cool since I added the hood vents, and got the engine burped. Sometimes, it seems rough at part throttle, mid-range rpm, and it's not as lively above 4k rpm as it was with the maximum fuel pressure and 19# injectors. I'm trying to get Hesco to respond on whether or not, the cam is normally as lumpy and lopey as it is in mine.

Oh, it's still getting 8 mpg at less than 500 miles on the engine. Engine has stopped using oil.
 
Final update. I read Cruzers bit on indexing the distributor. Didn't go through all the steps, just found TDS on #1 and put on a distributor cap with a window in it. The rotor was about half way through the #1 post. Rotated the distributor so the rotor was just past the #1 post. Made a huge difference. Decided to go back to stock injectors, got another set of 4-holers off of e-bay, and installed them. It runs like a raped ape. I had Bud's muffler shop install a Magnaflow to replace the generic turbo muffler I had put on, and fix the half assed stuff I had done to the exhaust. It sounds really good hitting 4k a block away. Hopefully my mileage will go up a bit from the 7 mpg with 22# injectors.

I might be tempted to get some roller rockers, it really does want to rev past 5k, but I think I'll leave it alone for awhile. It doesn't piss oil everywhere anymore, it runs really smooth from 800 rpm to 5k rpm and sounds good. Time to move on to other projects. :)
 
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