Stumbling, backfiring 1500-2000 rpm, Renix

[AIbandit]

Does it matter if I cut the ears off? Could have been done already lol.

Oh I misread cruisers guide. time to chop that stupid thing off.

 

[cruiser54]

You can get it right if you cut the tabs.........

 

[Ecomike]

Chop chop. LOL

 

[cruiser54]

Chop chop. LOL

No kidding.

 

[AIbandit]

Alright she fired right up, have to wait until tomorrow to see if it solved the problem.

 

[cruiser54]

Alright she fired right up, have to wait until tomorrow to see if it solved the problem.

what did you do?

 

[AIbandit]

Indexed the dizzy and adjusted it to where I think it's pointed on your picture. I'm thinking it was already fine before I started, but we shall see.

 

[CJR]

To me this sounds like a timing issue; either proper distributor indexing OR proper degreeing of the Comp cam with the crank. Are you sure the cam was degreed right for your stroker? My rebuilt/modified 88XJ runs a custom reground stock cam, from Comp Cam, as well.

Best regards,

CJR

 

[8Mud]

 

[Ecomike]

Well this is disturbing. I could swear mine is on the other side of that pin now, when I got mine perfect, but Cruiser54's web site shows this image below, so I guess my post below saying it was on the wrong side of the post/pin is wrong? Darn it, Now I need to go pull my cap and see which side its on, LOL. Damn this oldtimers disease shit. Now what was I just doing? LOL Now that I think about it I guess it needs to be almost past the #1 pin at TDC because it fires just before TDC, and the spark needs a bit of time to fire so ignore my earlier post about it needing to be on the right side instead of the left side of pin #1.

 

[Ecomike]

If his indexing does not solve it, he should re-read your comments below about lack of fuel. Isn't there an intake to head port overlap gasket mismatch issue for the HO intake on a Renix head? One that could cause intake leaks if not customized? Not sure I have seen a this combination before much less on a stroker?

How did you handle the transmission throttle cable to the AW4 adjustments? That controls AW4 pump pressure and ......

And did you mount a Renix TPS on an HO head??? You used a Renix throttle body on and HO intake???

Trying to picture it so I can help debug it.... Vacuum leaks are possible, but they should cause a high idle on the renix too.

Does it still have an EGR valve??? I hear Renix can run fine with out an EGR valve, but other rigs can have issues....

Yours being an 87 presents a special set of issues. The timing of the OEM cam, the timing chain gear and rotor position was a little off from the factory. There is a TSB about this.

After market cams, timing gears, can present some special issues.

Your bucking being mid range doesn't indicate to me it being a valve train/distributor (rotor) issue, I may be wrong. The typical cure for mid range detonation is to retard spark, hard to do in a Renix. Next best is more fuel.

Sounds more like it is running lean and you are getting some detonation at mid range. In effect too much air and not enough fuel. Try unplugging the O2 sensor and see what happens. Try the stock TB again. Renix (and pretty much all 4.0 injected engines) run pretty close to the edge of detonation anyway.

Vacuum leaks can also be a contributing factor.

 

[AIbandit]

I needed this in my life. I tried finding a good picture of it without luck.


I'll probably mess with it again at some point but she's running great. No more symptoms.

Thank you gentlemen.

 

[AIbandit]

If his indexing does not solve it, he should re-read your comments below about lack of fuel. Isn't there an intake to head port overlap gasket mismatch issue for the HO intake on a Renix head? One that could cause intake leaks if not customized? Not sure I have seen a this combination before much less on a stroker?
I have an HO (7120) head. HO header and 99+ intake.
99+ intake was probably the most annoying mod. It effected so much other shit for no good reason.

How did you handle the transmission throttle cable to the AW4 adjustments? That controls AW4 pump pressure and ......

I read somewhere about an HO cable to replace the renix one that was too short. It seems to work. Can't remember which year though
And did you mount a Renix TPS on an HO head??? You used a Renix throttle body on and HO intake???
Renix TPS on an a bored HO TB. It involved nylon spacers a dremel tool and a dab of jbweld for now.
Trying to picture it so I can help debug it.... Vacuum leaks are possible, but they should cause a high idle on the renix too.
I'm confident I don't have a vacuum leak I only hooked up like 3 things to vacuum and capped the 10 extra vacuum ports on the 99+ intake.
Does it still have an EGR valve??? I hear Renix can run fine with out an EGR valve, but other rigs can have issues....
nope no EGR

I was really thinking fuel too but being that it ran great at WOT I didn't think that could be it unless the HO regulator wasn't feeding enough below WOT.

 

[AIbandit]

Not sure I have seen a this combination before much less on a stroker?

I suppose she's "unique"

 

[Ecomike]

I was really thinking fuel too but being that it ran great at WOT I didn't think that could be it unless the HO regulator wasn't feeding enough below WOT.

The ECU ignores the O2 sensor at or near WOT, (and during rapid acceleration I think) and opens the injectors on a very rich feed mode!!!!

In closed loop mode the ECU uses data from the O2 sensor to control fuel feed. It uses TPS data and MAP data and CTS and IAT data to estimate the need for more or less fuel when you push or back off the gas pedal.

At a steady gas pedal position, as in a TPS fixed position, the ECU uses the O2 sensor in closed loop to add or reduce fuel rates!!!! So if it is only missing at a fixed 1500 rpm, I would look at the O2 sensor and wiring.

So it is important to determine if the problem is at a fixed TPS position, or while pressing on the gas pedal for more fuel.

TPS can have a bad spot between idle and WOT!!!

No ERG on this? Deleted or not?

 

[Ecomike]

Gotta love that it still has a well aged Renix closed system coolant bottle on it.

Unigue? Then you should name her Monique? LOL

What is the big silver thing on the right side?

I suppose she's "unique"

 

[AIbandit]

I've been getting a lot of shit for my cooling Lol!
It works! I have a Taurus fan otherwise it's unaltered.
Edit : power steering and trans have their own coolers too, if that counts.

Power steering Resevoir with the red top? Other things over there Hydroboost with an escalade master cyl.
coilover remote res. peaking through.

 

[Ecomike]

I have 4 Renix jeeps with the OEM closed coolant systems with the bottle in your photo. I was praising the fact you still have it even with a stroker upgrade. Mine have OEM fans, ZJ clutch on two, new all brass 3 row radiators on 2 of them. :clap:

I've been getting a lot of shit for my cooling Lol!
It works! I have a Taurus fan otherwise it's unaltered.
Edit : power steering and trans have their own coolers too, if that counts.

Power steering Resevoir with the red top? Other things over there Hydroboost with an escalade master cyl.
coilover remote res. peaking through.