Major issues, Running Lean and Detonation

[Black00Sahara]

My build is driving me crazy.

I have had the computer reflashed multiple times (B&G Chrysler) having the timing retarded, still seriously detonating when it warms up. Also running really lean. What should I start with ?? My local mechanic can't figure it out, or doesn't want to mess with it since its a custom engine issue.

I am running 93 octane.

2000 (OBDII) Wrangler TJ, from 4.0 to 4.6 build ended up after calculations at 10.2 compression ratio, Added 27# injectors.

[Cheromaniac]

Which cam did you use?

[Black00Sahara]

Well, I asked them for the brand name and model number but they just sent me the duration specks.... So I have no idea.

I think I need to get a list of everything they used.

[CobraMarty]

How do you know that you are running lean?

[Black00Sahara]

How do you know that you are running lean?

The mechanic was trying to figure it out and in the process removed the spark plugs and looked at them.

[Black00Sahara]

After reviewing a few forums and reading a lot of information I have come to something that I think seems logical....

Keep in mind this is a 2000 TJ with the OBDII

The adjustment may be needed to the Camshaft Position Sensor... Doesn't it tell the computer where the Camshaft is in relation to the engine cycle?

I am thinking (after reading) that setting the #1 piston to TDC and setting the CPS to even (toothpick method) is ONLY for a normal engine with a normal camshaft and such.

What do you all think?

[Black00Sahara]

*bump

Anyone think this is the right track?

[SilverXJ]

You can't tell much by looking at the plugs on an EFI engine, especially at idle or in closed loop. You can try to resynch the cam sensor, but if that is off you will usually have misfires. What cam was used and was it degreed in? Did you check the fuel pressure?

[CobraMarty]

How do you know that you are running lean?

The mechanic was trying to figure it out and in the process removed the spark plugs and looked at them.

You need to know for sure and the only way is with an Wide band O2 sensor and A/F ratio meter/gauge.

[tequila mike]

I had a similar lean problem.
Took it to a smog shop for an off the grid exhaust gas analizer test for $20.
Ask your mechanic for the exhaust gas analizer test results to confirm lean condition.
I ended up installing an afr meter i had laying around to fine tune and monitor it.
Still struggling with slight lean condition.
Hope this helps.
m

[superstingray77]

Do you have any exhaust leaks?
Does this model have 4 02 sensors like my 99 WJ California or just 2?

Cam sensor is used to directly control injector timing, so if the cam is not degreed in and the cam sensor is off it will cause funky issues with the mixtures and the PCM will hit closed loop mode and try to command 14.7 using 02 feedback. It does stand to reason that if the cam is wildly different than the factory grind it will require a different sync procedure, however getting it close it should run OK.
How much compression does this puppy have?
Have you checked the TPS voltage and the "smoothness of the TPS" transition through the full throttle range?
What plugs is it running? Perhaps run a colder heat range to pull more heat from the chambers, and DO NOT USE Platinum rofl.
Any blockage in the cats or exhaust system will cause a major rise in EGT and detonate.

When I had my 4.7 running the first time (before the cam failed at 2k miles) i had a lean condition with a tip in stumble off idle only after warm up. It was caused largely by an incomplete weld seam in the Banks header right before the rear 02 bung at the 3 way collector. By welding that up and fixing the leaks it helped tremendously. Fuel pressure should be around 51 psi. Did you install 24# injectors that are for CERTAIN flowing 24# at the rated PSI, some of the injector sales I have seen on the bay advertised higher flow #'s by using a higher rail pressure rating. For example my 24# flow 27# at 51psi and I have seen them advertised as 27# injectors which they clearly are not. I think 43.5 is the standard PSI for flow rate.

The larger cams will cause the idle vac to be low which will run the engine rich and retarded but as you tip in the throttle the signal rise will cause it to want to lean out under load. All that should be fixed in the programming though.

Good luck man I know its frustrating to spend all this money and time and not enjoy it... or have the damned thing blow up after 2k miles.

[Black00Sahara]

So i finally got all the information I needed. Here it is.

I did check and there is an exhaust leak way back at the muffler? Does that count? Its where the PO hit a rock and crushed the weld on the back of the muffler, its not noisy so I didn't notice it at first.

I just ordered a new heater core and high flow 2 core 1.5 inch width radiator. I will be purchasing a FlowKooler water pump also to try to move a little more heat out. Its currently running about 220 degrees after it warms up. I shut it down after it gets that hot, so I can't tell if it will get hotter. I am scared to let it go any higher.



Block was taken to .020" over and block and head both had .004" taken off in order to ensure they were perfectly flat.

Crank casting number is 3235477 OEM Jeep 4.2L crank

OEM Jeep 5.875" center to center connecting rods casting # 707

.020" over sized Speed Pro Coated Hyper. pistons (piston to wall clearance built into pistons) #p3071

.020" over speed pro factory replacement rings #s38816

Engine Tech camshaft #es242 .408" int/.414" exh lift, and duration @ .050 lift 188 int/190 exh

Felpro gasket set factory replacement. I don't have the head gasket part number anymore, but it is an OEM style kit.

The Compression Ration calculates to 10.2

[SilverXJ]

An exhaust leak that far back wouldn't effect the O2 sensor. What is your fuel pressure and what injectors are you running? Was the cam degreed in?

You should not be running that hot with a stroker.

[Cheromaniac]

Block was taken to .020" over and block and head both had .004" taken off in order to ensure they were perfectly flat.

Crank casting number is 3235477 OEM Jeep 4.2L crank

OEM Jeep 5.875" center to center connecting rods casting # 707

.020" over sized Speed Pro Coated Hyper. pistons (piston to wall clearance built into pistons) #p3071

.020" over speed pro factory replacement rings #s38816

Engine Tech camshaft #es242 .408" int/.414" exh lift, and duration @ .050 lift 188 int/190 exh

Felpro gasket set factory replacement. I don't have the head gasket part number anymore, but it is an OEM style kit.

The Compression Ration calculates to 10.2

It looks like you have a Melling stock replacement camshaft so the cam position sensor should already be properly synched if you used the toothpick method.
You've quoted an SCR of 10.2:1 but according to my calculations it's actually 9.7:1. That'll make the DCR pretty high with the cam that you're using.
You really need a wideband O2 sensor and gauge so you can find out what's really going on with the AFRs. My feeling is that your engine's running lean at the low rpm where the stock computer is locked into a 14.7:1 AFR at WOT. I somehow doubt that the injectors you bought were 27lb'ers so can you give us the part no. just to check?

[wjtom]

stock spark plugs?if so get rid of the extended tip.