crazy for the 4.7

Hello Moses. Replacing the MAP sensor and the bank 1/1 O2 sensor did not correct my problem. Bank 2 O2 has been replaced previously. I did another live scan and have found the fuel trim is possibly in a rich condition. The long term fuel trim is negative (-7.2 to -12.5) and the short term fuel is 0 to -3. I think I narrowed it to bank 1 drivers side, but not completely sure. Now the fuel filter and the k&n air filter are old so I will change them , however unless its a PCM issue, I'm leaning towards a leaking injector. Can I test for a faulty injector without removing them from the truck. The motor runs really well other than this idle issue, so I'm not thinking coil pack, but I would like your opinion. Also how different is the PCM tables in drive with a load verses in park. The issue only occurs in forward gears not in park (idles down from 650 RPM to 450 Rpm).

Well I replaced the Map sensor today and although the jeep is running better, the condition still exist. An area of improvement is the transmission is shifting much firmer in all rpm ranges. I did not change the oxygen sensor yet (has not come in yet). My hope is that the o2 sensor is the fix, we'll see. Moses I agree with you in that I also only purchase Chrysler /jeep products especially when it comes to the sensors. Its worth spending a little more for the confidence that the issue will not soon return. Moses I do want to ask you, I know the TPS sensor is for the most part plug and play. However can the TPS be fine tuned via the voltage to find the engines peak performance (sweet spot). I have done this in the past with other brands but you need to know what the voltage numbers are. Are you aware of tuning the jeeps in this way.

I meant to respond to you Moses in my previous comments but was distracted. I have had ALL of the issues with my 99 Grand (WJ) that all others have had throughout the years. I have also read through countless forums in search of solutions and what I find a lot is everyone has had the same questions but cannot find true and accurate resolutions. As far as the heads, so far no issues. Cam changes are not extremely difficult, and upgrades are available. A good machine shop can address and fix the valve guide issue. The only issue I have with the 4.7L are the ring lands are to tall (close to the top of the pistons). Poor set up for performance especially boosted applications. And also not much in after market choices for the Jeeps (more so for the Dakota and Durango market). The 4.7L does not like heat as stated and cooling is a priority. The electric fan is huge and a constant issue. The tow package includes the mechanical clutch fan and the electrical fan (possible upgrade option). Also aftermarket transmission coolers anything to keep the temperatures down Always get Chrysler fans and relays. This is a huge job to replace them and not one you want to do twice if you can help it. Also I recommend upgrading to a larger aluminum radiator (two or three core). Helps a ton especially in hotter climates with the A/C on continuously. The truck runs five to ten degrees cooler since doing this. As for the HVAC my dash as been out three times since new. Mostly for the heater core and the blend doors changes. I would change the Evaporator also if you have reached this point of repair. The HVAC control switch is still the factory switch and has not been a problem as of yet. Although I do not have the dual climate control switch I believe you are referencing. I have found the parts yard is a good source for replacing them cheaply if need be. Other than that the system has worked as advertised so far. The WJ is a great truck and the 4.7L V8 does not get the praise it deserves and unfortunately there is not a lot of aftermarket for them (for the motor heads out there). I would be happy to assist anyone in answering or discussing any topics or issues relating to the Jeep Grand Cherokees. Thank you all in advance for the opportunity to address my concerns as well, this a great forum with a lot of experiences being shared.

Hello fellow jeepers. Update, I had a local transmission shop (one I trust) just inspect the transmission mostly to eliminate the transmission as a cause to my issue. Also due to the high mileage an eval on a fluid change with possible upgrades possibilities (reprogram kit, solenoid etc...). The transmission is great no worries and no TCM codes found by the transmission shops scanner. Therefore safe to say the transmission is not causing my low idle problem. Background. This issue started when I replaced my catalytic converter and also upgraded to a single three inch exhaust. The truck already had prior, an after market Y pipe and a three inch cat converter, but also had a cat back borla (2.5") exhaust. The catalytic converter was bad so I replaced it with the same converter and upgraded to the larger exhaust pipe (cat back). The 4.7l v8 works really well with this setup (single pipe only). Soon after doing this is when the issue began. Eliminating the transmission I began to check the map sensor as Moses suggested. What I found was the engine is making 19lbs of vacuum at idle. However the MAP sensor voltage was all over the place and at intermittent times only reading 4lbs of vacuum. Also the 1/1 (upstream) O2 sensor was reading a steady voltage at idle. While driving the truck, the O2 sensor was working properly (I don't have the voltage readings) but it did read high and low as it should. At idle it would read the same voltage and did not change. I will check the voltage to the Map sensor to eliminate a wiring issue. And since the O2 and MAP sensor are related I may change the O2 sensor as well. Additionally I don't think at this point the truck is loosing vacuum, so I don't think the cause is vacuum related.

Thank you Moses for the quick response to my concerns. I have an appointment in the morning with a local transmission shop to check for transmission codes via the TCM and I will post the results tomorrow. I would be glad to assist any members who may have any issues which pertain to the 4.7l V8 or the WJ's in general. For reference the transmission has no issues and the motor runs really strong despite the high mileage. Therefore the cause has not been obvious.

Hello everyone, I have been troubleshooting various electrical issues for months. I am fixing the issues as the occur, however one issue I cannot seem to determine the cause. A 1999 Grand Cherokee WJ with an intermittent low idle complaint. The idle drops to 300 rpm in drive only. I currently have no trouble codes. I have checked all sensor voltages and they are all correct. I did change the TPS and the IAC anyway, but the issue is still occurring. Not sure where to go from this point, so I really do appreciate any help or suggestions you can provided.